jam

a problem situation

Example:

We are in a jam.

jaw

a chat

Example:

They had a jaw about the new boss.

jerk

a stupid person

Example:

That girl in accounts is a jerk.

jiffy

very quickly

Example:

I'll be with you in a jiffy. I have one more short call to make.

john

the toilet

Example:

Excuse me. Where's the john?