someone who doesn't smoke in the same room or apartment where their computer is might type this in conjunction with BRB to indicate that they're breaking from whatever online interaction they having with another person or persons over the internet for at least the duration of time it takes them to smoke a cigarette. ~ 4-10min.
SMK ROFLCOPTER! XD
When an individual laughs so hard and begins to smack their knee.
That girls outfit made me SMK
Judy: (after laughing out loud) "SMK"
Jane: "what does that mean Judy"
Judy: "I'm smacking my knee because you have me laughing so hard!"