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1.
1) verb- Drop a glock (or drop the glock, or whatever) has a similar meaning to bust a cap. The word comes from the streets. Gangstas in some areas will tuck or strap a handgun, usually a nine or glock, in their sleeve, up by their shoulder. If a situation arises where a gun is needed, the gangsta can snap his arm in a downward motion, thus freeing the gun and letting it slide down into his/her hand. Now the gangsta is ready to bust a cap.

2) verb- Used as a threat implying that the person is willing to do what the above definition describes.
The rival gang member pulled out a nine so Jon was forced to drop a glock to protect himself.

Fool : "Man, your momma is fat."
P.I.M.P. : "Yo Fool, don't make me drop a glock on you!"
by Doobie Smokes You May 07, 2005