SMG

Exclamation:
shortened version of "slap my grandma"
used in place of "lol" to make you seem more "hip"

hahaa omg bro that's hilarious smg

SMG

Stands for "slower than manual gearbox"

Often found in BMW E46 M3's in the era when BMW could not produce a proper gearbox

Person 1 : My E46 m3 has an SMG box

Person 2 :Oh that's a shame

SMG

Son of a Motherless Goat

SMG, that hurt! Son of a Motherless Goat, that hurt!

SMG

Smacking my gum. Derivative of SMH.

Used to express:
a) Oh, really?
b) Mhm. That sounds like crap.
c) I don't believe you.
d) Shut the hell up.

Person A: I totally got three million points on BrickBreaker yesterday.
Person B: SMG.

SMG

a variation of suck my balls, this means Suck My Gonads. when used as a clan tag in cod (call of duty) it can be interchangeable with the term Sub-Machine Gun, for those of us who enjoy using weapons such as the p90 on xbox live.

SMG just pwned you with a p90, bahaha SMG.

SMG

Shaking my goods

Did you see me SMG out there?

SMG

An acronym for Sick Mack Game.

Man, Tim really has an SMG lately, he's hooking up with everyone.