The opposite of a greeting.
Most often used when talking on a cell phone or 2-way radio.
References Capt. Kirk of Star Trek fame, when he would conclude all dialogs from the planet to the Enterprise with this phrase.
Also popularized by rapper Flavor Flav.
While talking on your cell phone:
"Okay, bring me two sam adams
and I'll meet you in the DnB Room
around midnight. Kirk out."