1 definition by Alejandro The Great YouTube

A great comeback or a phrase that will wreak havoc. This phrase and be used to simply annoy someone or to say for the heck of it.Also it can be used in a conversation.
1)Ruben:Your a butt cheek

Tom:I know you are but what am I?

2)BOB:I'm going to be Albert Einstein

Rick:I know you are but what am I?
BOB:Beats me it's up to you
Get the I know you are but what am I mug.