Commonly refers to the three bags of milk offered at local grocery stores and convenience stores alike, or, any product offering that comes in a 3-bag pack.

Alternatively, the act of getting teabagged by one who is born with three testicles, or getting tea-bagged by 3 people at the same time.
India: "Alfredo, pick up some milk on your way home."
Alfredo: "Sure, a carton or tri-bagger?"
India: "Definitely tri-bagger."

Alternative:
Kid with 3 balls: "I just tri-bagged your mom"
by Amarci_ano July 28, 2010
Get the Tri-bagger mug.