When one plays through a video game (usually an RPG) with no equipped armor or other stat boosters. Makes for an extremely challenging and interesting gaming experience (especially because your character often will be naked without equipped armor/items).
Gamer 1: Have you tried out Dragon Age: Origins yet?
Gamer 2: I got it the day it came out! I've already completed a naked run!
Gamer 1: Really?!
Gamer 2: Yeah, it was VERY challenging, and it was funny to watch my character run around in his skivvies.
Gamer 1: Sounds awesome! I might have to play in my briefs along with my character.
Gamer 2: ...
An event at UC Santa Cruz that takes place every year the night of the first rain. A group of students goes around from college to college, collecting more crazy people on the way, in nothing but their birthday suits.
I couldn't believe my eyes when a member of the Naked Run came running into my dorm, trying to recruit more insane people.
The standard consequence of losing a beirut/beer pong game very badly. The losing team is required to run naked around the outside of the building in which the game is being played. Depending on house rules, a naked run rule may be enforced either when a team loses before making it to their first re-rack (6 cups left) or when a team does not sink a single cup in an entire game. This rule is often not enforced in a game where all players are male because that would be considered "too gay."
Steve: "How'd you guys do in the Sigma Chi beirut tournament?"
John: "Not too great. We lost to 'Wet Balls' in the semifinals."
Steve: "Man, in every tournament there's a team called 'Wet Balls.' So unoriginal."
John: "Word to your mother. But at least we got to see Vicky and Sarah lose a game by 9 cups and do a naked run around the building."
Steve: "Hell yeah! Vicky is pretty hot. I would have loved to see those things bounce around, if you know what I mean."
John: "Yeah it was pretty awesome. Skeet skeet!"