The universal definition is "to get something done," but it can be stretched to mean "to close the deal," "to sell," etc. The opposite of procrastinating.
Person 1: I'm almost done with this report! I'm so close to cinching the peet!
Person 2: Yeah, dude, cinch the peet!
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.