1. Expression used to denote how much time an individual has spent firing their weapon.
2. Also used to describe the time a man spends firing his gun in female cavities. This is my rifle, this is my gun. This one's for fighting, this ones for fun.
Gun = dick
Rifle = weapon for the killing of animals, foes, people, or just for fun.
"One of the odd things about the Army is how little actual trigger time you get. You carry your weapon around a lot, but aside from periodic qualifications or occasions where it gets entirely too exciting you don’t shoot very much."
"Yo, I wuz gettin' some major trigger time with your ex last week."