An urban slang used to replace shotgun , vinchester , etc.
Became a popular word in a popular game called "Fortnite" , battle royale copy of a copy of a copy.
1. Last match i got 5 kills ONLY from a pump-shotty!
2 No fair! He killed me with the pump-shotty!
In Most online FPS's there is generaly a pump action 12 gauge. This gun is usualy slow and inaccurate. In counter strike, this weapon if killed by it is a humiliation.
One who is well skilled in the art of the Pump Shotgun in games such as Counter Strike, and jump around while killing people in the air...much like a ninja. Thus the term, Pump Shotty Ninja.