Typically found on college campuses. A runner is an individual who spontaneously takes of in a wild gallop for no apparent reason. This individual can most commonly be seen in the late hours of the evening when few people are outside.
I was walking with my girlfriend last night and a runner came down the sidewalk. After stopping in the middle of the walk, she proceeded to round the corner and fall.
The member of a group that goes out to get needed supplies, i.e. alchohol, food, ice, condoms, cigarettes, etc.
This person's effort acts as a deduction against share tax, and he/she is usually the initiator of insies.
Mary: We're outta smokes and beer. I've only got $5 but I'll be runner if anyone wants insies.
Everyone: Okay
Mary: I need your share tax.
Joe: Here's another $10.
Jim: I'll give another $10
Jane: I'm giving $20 to cover the rest of Mary's share 'cause she's the runner.