Is an acronym standing for "Shit My Pants and Cry." Something that is either so funny, sad, or gross that it would cause them to shit in their pants and cry.
When John followed that girl around all day and finally had the courage to go and talk to her only to find out it was just a dude with long hair, I almost SMPAC 'cus it was so damn funny.

omg, that video Hatchet vs. Genitals was so disgusting and sad that I almost SMPAC!

John: Chris and Tommy came over last night and I was so tired I knocked out. I woke up with a carrot stuck in my ass!
Sylvester: SMPAC!
John: STFU you wouldn't be laughing if it happened to you!



John: Damn! I was walking home and I saw Eddie get hit by a car. His friggin' guts and brains sprayed all over the sidewalk!
Sylvester: S M P A C
John: Yeah...that was some crazy ish...


John: You missed the funniest shit ever! Paco just tried to light his fart but ended up sharting on himself. I was LMFAO
Sylvester: naw...more like SMPAC. that shart is hella funny!
by chutrain August 6, 2008
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