Usually pronounced when mumbling. The description of weed when talking about it in public. can also be said while making a "2-puffs on the joint" gesture
The Boy: Yo dog, whats good?
The Man: Nothin. What you doin?
The Boy: Not shit.
The Man: You wanna go behind tha dumpster n smoka lil bitter dat sum sum?
Tina: Do you smell skunk
Ed: Skunk? You talkin as in the animal? Or you talkin bout you smell sum sum?