"shake my head" or "shaking my head"
people also think its
"santa monica highschool"
person #2 "nothing just doing situps. i just hit my head with my knee going up"
person #1 "smh"
girl 1: "what school do you go to?"
girl 2: "i go to smh. and you?"
girl 1: *confused*
To be said after something ridiculous or embarassing (to someone else) happens.
Essentially telling someone that you need to have your head "steadied", in reference to the head shaking in dissaproval or moving with laughter, because what has just occured it so outrageously funny or embarassing to the other person.
This can be pronounced verbally as "smhhh" or "smuh".
Chick: Can't say the same bout you.
Other Dude: SMH (smhhh)!