icky: not good; very unattractive.

Christine decided not to walk into the muddy water saying it looked too icky and smelly.

I.D. : an abbreviation for "identification."

You will need a student I.D. if you want to get into the football game for free.

iffy: questionable; uncertain.

Whether or not the project will be completed on time is kind of iffy at the moment.

in: participating; a part of a group effort. (used with "be" and "count (one) in")

If everyone wants to get a pizza, then I’m in. (You can count me in.)

in a jiffy: very fast.

I’ll have your order to you in a jiffy.

in line for: next.

Nguyen is in line for a big promotion at work.

in no time flat: very quickly.

We ordered some Chinese food and it was delivered in no time flat.

in one piece: all together; intact; without injury.

Somehow 20 people came out of the burning airplane in one piece while 145 others died.

in one’s pocket: to have a person’s loyalty.

Jennifer used to be in Pablo’s pocket, but now she’s seeing other guys.

in the loop: to have information that others might not have; to have some degree of power or influence.

I’m no longer in the loop at work.

in the doghouse: in trouble; to experience a lot of difficulty with another person.

I’ll be in the doghouse if I don’t bring my wife flowers on Valentine’s Day.

in the money: to suddenly have a lot of money.

After her uncle died and left a big inheritance, Lee was in the money.

in the works: something that is being planned right now; as we speak.

The boss doesn’t want to give us all the details right now, but he says that something big is in the works.

IOU: a note promising the payment of money–stands for "I owe you."

Bedros wrote his landlord an IOU when he couldn’t pay the rent.