The area of perspiration on an individual's pants/shorts in the butt-crackal or taintal region made visible to the eyes of the surrounding audience; most commonly associated (but not necessarily) with strenuous activities - such as working out.
Hey dude. . . before we go out in public, you gotta do something about that gnarly fitness stain you have goin' on down there! Does that not bother you?
by Stupidjerkheadface April 9, 2016