Cheese

A word you say at random times. Why? You don't know. You just say it.

You're just sitting at your computer looking thru Urban Dictionary and you just say "Cheese". Then you carry on with your day. As if nothing just happened.

Or you're with your friends and you random say "Cheese" and you have to tell them why you just said it out of nowhere.

John: Cheese...
Mike: What?
John: Oh uh... Nothing.