In case
If, if something should happen.I will take my umbrella in case it rains.
In care of (someone)
Something is sent to someone at someone else's address.My income tax refund was sent to me in care of my company.
In between
Located in the middle of two things or states.My friend is in between jobs at the moment.
In bad taste
Not suitable, offensive.The jokes that the man told at the dinner were in bad taste.
In bad faith
With bad or dishonest intent.The man was bargaining in bad faith when he tried to buy the car.
In awe of (someone or something)
Fearful and respectful of someone or something.The children were in awe of the firemen who came to visit the school.
In arrears
Overdue (used for bills or money), late.I have never been in arrears with my bill payments.
In arms
Armed, angry and ready to fight.The workers are in arms since they learned about the wage decrease.
In any case/event
No matter what happens, surely, without fail.I may not be able to meet you next week but in any case I will give you the books before then.
In and out
Coming in and going out often.Our boss has been in and out all day but I do not know where he is at the moment.