treadmill vag
(1) referring to a woman's vagina after she has been working out or engaging in any kind of activity that may cause perspiration

(2) a sweaty vagina
example (1)

girlfriend: i just ran 5 miles and i still have so much energy. what do you say we burn some more calories in the bedroom? wink, wink.

boyfriend: how bout you clean up that treadmill vag and maybe i'll consider it.

example (2)

guy 1: dude, i tried to go down on my girl last night after the club and her pussy smelled like week old sushi.

guy 2: haha. you were experiencing treadmill vag bro.