To be caught unware. Suprised. Modifiers include "down around the ankles".

The penalty for losing a game of 8-ball (standard pool) without potting a single ball is to walk around the table with one's pants down (or skirt up), according to official pub rules. This counts for any loss, including accidental sinking of the eight ball.

a phrase used to describe something especially shocking and/or awesome, a more extreme version of 'hands-down'.

Alternative to the outdated term "Hands down" to convey a statement with absolute conviciton and certainty. "Pantsdown" was originally coined by centaurs in Middle Earth due to their physical inability to wear pants despite the group's strong desires to do so.

When she gets turned on and undos your belt let's down your zipper and pulls down your pants or your shorts or your sweats or your underwear to play with your private parts

Used to substitute the age old saying "hands down".

Old fashioned humor that is corny but still gets a laugh as in the Vaudeville skits when a man's pants drop.