An expression of exasperation when someone should have heard of something already based on its wild popularity. Having this phrase used on you implies that you should use an internet search engine to look it up to save yourself from further embarrassment.
I have a question. - person 1
NO YOU CAN'T HAS CHEEZBURGER! - person 2
What? No, why would I want a cheeseburger, that makes no sense? - person 1
Omgoogle... - person 2
Oh...guess I should google it. - person 2