Acronym for "Shove Mom Into Wall."
Quite silly and pointless. Suggestion: don't use around mom so she won't know what you're talking about.
Hey Annie! OH, I'm sorry, Hi Annie's Mom! Hey Jill? Got something to say to my mom? OH YEAH!! SMID!
(Annie's mom face looks confused and anxious to find out what on Earth Smid means.)
WAAAAAAAAAHHHMMM!!!!! OH YEAA!! SMID, YOU NEVER LET US DOWN!!