Definitions by Klitzke

F.L.S. 

1.)A vague, fake medical condition that sounds serious but actually means that you Feel Like Shit.

2.) often used to call out of work, to aviod someone you don't want to hang out with, etc.

"Dave can't come in today, his F.L.S. is acting up again."

F.L.S. by Klitzke May 18, 2008