A Pathetic attempt at an Insult, Usually by immature or young people.
Or, Sometimes used to be sarcastic, annoying, or otherwise.
Sometimes followed up with an "OOOH!! U JUZT GOT BURND LOLOLOL" Kind of statement.
Sometimes spelled in chatspeak like:
Immature/Annoying Your Mom definition:
Kid: "Is there any continent larger than Asia?"
Other Kid: YOUR MOM!! LOLOLOLOLOL
Random Kid: BUUUUUURRRN
The "Pathetic" Definition Example:
Guy: Your such a loser.
Second Guy: Your Mom!
Guy: That comeback is stupid.
Second Guy: UR MOM!!!11!
Sarcastic Definition example:
Dude:Hey Dude what's up?
Random Dude: LOL YOUR MOM.
dude: HAHAHAHA /sarcasm