A naked lap happens in a drinking game/bar sport when one
person achieves the winning score while the other
person fails to make some minimum number of points.
In ten-cup beer pong for example, if seven cups remain on the table at the end of
the game, the team with seven cups left has to run a naked lap.
In pool, a 7 Ball Loss (pub/taven pool rule) is usually grounds for a naked lap.
Many rules have been established for other common sports such as darts, foosball etc., but the threshold for naked lapping tends to vary from venue to venue.