The act of one giving themselves an over-the-pants handie, whereas they are either unable or too lazy to pull their pants down and masturbate correctly.
"This morning at work John was totally caught slacking-off under his desk."
The verbal greeting equivalent to a hand shake. "Smacking" comes from the sound peoples hands make when they slap hands during a handshake. 'Off' is the from the saying "Whats poppin off" which means "whats going down? or whats up?". Smacking off is the greeting that is a combination of the two, a handshake and a question rolled into one saying, used as a greeting amongst friends or associates.
Person 1 : Smacking off G? What you been up to lately
Nickname given to bales of marijuana thrown overboard or out of airplanes. Origin is reportedly from members of the US Coast Guard in the area of Southern Florida.