The uncomfortable feeling of a sweaty anus, usually experienced by those working outside during a hot and/ or muggy day.
Man, I can't take it anymore! I can't wait until break and then I can go take care of my terrible case of sweanus!
Sweanus.....after a workout, or hot summer day, or some steamy intercourse, the moisture that develops in the crack of your ass, is called, sweanus. More often than not, it refers to someone in the negative....because they may have actually just not showered in days, therefore creating a funky odor from 'back there'. Combines the two words sweaty and anus.....sweanus, VOILA!
Scene: Walking down the street with your friend, behind someone with a line of moisture on their pants (ya know, on the 'fault line'):
"Hey man, check out the sweanus on that back".