Internet acronym for "Funniest Moment Of My Life." It is generally used as a mockery of the acronyms ROFL, LMAO, etc. People don't literally roll on the floor laughing or laugh their a**es off.
FMOML is a sarcastic over-exaggeration of moments that are seen as "funny," but actually aren't.
<nerd>I had the coolest dream last night that I won the lottery! LMAO!
<nerd>Yeah! Isn't that so funny!?
<jock>... Oh, yeah. Totally FMOML.