Phrase used by people who do not desire to hang out for the day. Often used to avoid offending someone when they already have plans, do not want to hang out with the asker, or really just want to stay home. Often followed by three periods (..) to show false/real remorse.

Friend 1: Hey, wanna go see Yogi Bear?
Friend 2 (to himself): That idea sounds hella stupid 
Frined 2: No thanks, I'm staying home today...

 

Urban Dictionary