I'll eat my hat
(spoken) I really don’t think that will happen; I will be really really surprised if that happens

– example

“She hasn’t gone to any of the lectures, and her essays have been awful. I’ll eat my hat if she passes that test.”

“If Scotland beat Brazil I’ll eat my hat. There isn’t a hope in hell of them winning.”

the icing on the cake
the perfect thing to complete an already good thing

– examples

His birthday had been perfect: a trip to the zoo; a meal with friends; and a night at the cinema. The icing on the cake, however, was when Anne gave him a kiss good night.

“All the best people are coming. And, well, if you could too that would be the icing on the cake.”

if it ain't broke, don't fix it
(usually spoken) if there is no problem, don’t change anything

– example

“I know we had some concerns about the best way for this project to continue, but I say if it ain’t broke, don’t fix it. Let’s leave it for a while and see what happens.”

in a fix
(also ‘in a jam’)
in a difficult situation; how to get out of this situation seems very hard

– examples

After Dave said he was thinking of quitting the company, Philip found himself in a bit of a fix: should he tell the boss and help the company, or respect Dave’s decision?

“Could you help me out? I’m in a bit of a fix – I need someone to cover for me at work while I go to the hospital.”

– “I could speak to him if you want.”
“Oh no, no. I don’t want to put you in a jam. It’s my fault.”

in a flash
really quickly; almost immediately

– examples

Dave saw the woman reach her hand into the old man’s pocket, then take out his wallet. In a flash, he was after her, chasing her down the street, calling for someone to call the police.

“It was going well until I saw Dave arrive. Well, I was out of there in a flash – there was no way I was staying to listen to him.”

in a nutshell
in short; the main point (of a longer point) is…

– examples

The game against United was City’s season in a nutshell: a good start, followed by a poor ending.

“The conference was cancelled, and I thought you guys might be lonely without me.”
“Does that mean you’re coming with us?”
“In a nutshell, yes.”

in a pickle
in a difficult situation; in a messy situation from which you might need help

– examples

“I’m in a bit of a pickle, so I’m wondering if you could help me out: my boss has told everyone to work overtime this weekend, but I promised I would take my sister around town. Could you do that for me?”

in a tight spot
in a difficult situation

– examples

The rise in their neighbours armies has left them in a tight spot: do they spend more on defence, or concentrate on their own economy?

“I’m afraid your actions have left me in a bit of a tight spot. I would like to keep you, but the board is expecting me to be tough.”

in a rut
in a boring habit; not finding anything new or exciting

– examples

Anne had reached her late 30s and found her life was in a rut: going to work, coming home, watching TV. There was no romance, and no fun. She needed a change.

“Don’t worry about it too much. You’re in a rut, that is all. You’ll get a job soon.”

in (somebody else's) shoes
imagining if you were someone else; imagine if you had to live someone else’s life

– examples

After spending a day in his boss’s shoes, Dave realised it was not an easy job, but that if he worked hard he might be able to do it.

“Imagine if you were in my shoes: what would you do? They way I see it, I don’t have much of a choice.”

in cahoots (with somebody)
to be working with someone to beat someone else, or cause someone trouble

– examples

Dave was paranoid. They were all in cahoots – all of them! – wanting to bring him down, talking about him. He had to escape.

“Of course you would say that: you two have been in cahoots since the very start! I should never have trusted you.”

in dire straits
in real trouble; in serious difficulties (often financial)

– examples

The company is in dire straits, and has until the end of the week to find some new investment.

“You’ve got to help me, I’m in dire straits: if I don’t get them the money by this weekend, they’ll take my house.”

in cold blood
to do something (usually very bad, such as killing) with no emotion

– examples

Although Mr. Smith claimed he was innocent, the jury found him guiilty. When sentencing, the judge said the murder had been carried out in cold blood, and gave him 25 years.

in dribs and drabs
a little at a time; not all at once, but very small amount followed by very small amounts

– examples

At the beginning customers came in dribs and drabs, but now there is a steady flow.

in droves
a lot at once; a very large amount arriving or leaving at the same time (usually people)

– examples

Last year the festival did poorly due to the weather, but this year the people arrived in droves.

Voters have lost confidence in the party and are deserting it in droves.

in full swing
not at the start, but the busy middle; things happening at their most busy; in full effect

– examples

The party was already in full swing when Dave and Anne arrived.

in high spirits
in a really good mood; in a party mood

– examples

100 000 people arrived on Princes Street, and in high spirits they welcomed in the new year.

“You seem in high spirits today? What’s up? Is your wife on holiday or something?”

in hot water
in trouble with someone

– examples

“I had better go home if I don’t want to be in hot water with the wife.”

in league with (somebody)
working together; in a partnership (often to do something bad)

– examples

There were times during that marriage when Anne thought Philip was in league with the devil: he was so cold and cruel to her, and didn’t seem to care at all.

in (my) book
in my opinion; according to my thinking

– examples

“You were rude, and unhelpful. In my book that is enough reason to fire you, but the bosses are going to give you another chance.”

in (somebody's) bad books
out of favour; not liked because you did something wrong

– examples

Ever since he met his ex-girlfriend for lunch Philip has been in his wife’s bad books, so tonight he is taking her out for a surprise meal to say sorry.

in one ear and out the other
to forget immediately because you weren’t listening properly; heard, but ignored

– examples

“His mind is always somewhere else, and everything I tell him goes in one ear and out the other.”

in over (my) head
To be in a situation more difficult than you can cope with
(from the idea of drowning in water too deep for you)

– examples:

“I’m beginning to wish I had never taken on this new project; I’m in way over my head, and I’m not really enjoying life.”

in (somebody's) pocket
A person ‘owned’ by another person; to be completely controlled by someone

– examples

The newspaper owner had the politicians in his pocket.

in (this/that vein
(also ‘in a similar vein’)
to do something in a similar fashion; to do something in the exact way something was done before; ‘along those lines’

– examples

He has been working very well so far this year; if he continues in this vein he shouldn’t have any problems getting the score he needs.

in the bag
Guaranteed success in a project

– examples

“3-1 up with two minutes to go? I think this game is in the bag.”

in the clear
Out of trouble; Finished with, or avoiding, current troubles

– examples

“I was a bit worried that we were going to be caught, but I think we’re in the clear now.”

in the dark
Having no knowledge of a situation

– examples

“I’m completely in the dark on this, so you will have to explain what has been happening.”

in the doghouse
to have someone annoyed at you for a while (particularly people you know or love)

– examples

He has been in the doghouse ever since his girlfriend found he had been calling his ex.

in the flesh
meet the person, rather than on the phone or via a computer

– examples

– “I’ve always enjoyed watching him on TV, but meeting him in the flesh was a great honour.”

in the hole
owing money; in debt

– examples

Dave has a gambling problem, and he was $1000 in the hole before he finally gave up and went home.

in the long run
in the more distant future, rather than the immediate future; thinking further ahead than the near future

– examples

The company lost money this year, but the investments they made should help it in the long run.

“You’re mad at me now, but you’ll thank me in the long run.”

in the loop
in the circle of people getting given information on something

– examples

“I’ll only let you take over the project if you keep me in the loop as to how things are going.”

in the pipeline
in development; being planned

– examples

The company has been one of the biggest names in developing new products, and the word on the street is they have another great idea in the pipeline.

“Don’t worry about me losing my job: I have a few other ideas in the pipeline.”

in the same boat
in the same situation as someone else

– examples

“Sorry to hear about you not getting into the university you wanted, but you’re not the only one; there are plenty of people in the same boat.”

in the zone
doing something very well; on a run of doing things very well; to be really concentrating on something (not getting distracted by anything else)

– examples

– “Don’t disturb him: he’s in the zone at the moment. At this rate he’ll be finished by the end of the day.”

in turn
equally, or to the same extent

– examples

“I borrowed some money from him, and he in turn borrowed it from his friend.”

in two minds
Undecided; could decide one way, or the opposite

– examples

“I’m still in two minds whether I should go to the party. Really I should do some work.”

in (your) element
in a situation with which you are very comfortable, well practiced, or an expert

– examples

Ever since Anne moved to Australia she has been in her element; she loves the sunshine, and is really enjoying her new job.

(know) the ins and outs
to know everything about a subject

– examples

“We need to hire an industry expert, somebody who knows the ins and outs of the sector and can help our company grow.”

(the) inside story
the story that the public doesn’t know (but people involved do know)

– examples

The company says everything is OK, but the inside story is that they’re struggling for money.

The magazine this week is very interesting: it has the inside story of the wedding.

(disappear/vanish) into thin air
to vanish; disappear so nobody can see it or know where it went.

– examples

The magician just seemed to disappear into thin air.

(rule with) an iron fist
to rule with complete control, strongly crushing any alternative ideas or actions

– examples

For twenty years he ruled the country with an iron fist, destroying his rivals and throwing protestors in jail. Only when he died did the people feel some relief.

itchy feet
to begin to want away from an overly-comfortable situation; to begin to want to move on

– examples

At first he thought he could stay for another year, but it was not long before he got itchy feet; he wanted to explore the world, not sit behind a desk.