The presence of perspiration soaking through one's shirt located under a fat man's breasts, much like that which occurs in the arm pit.
In a hot college basketball stadium:

Student 1: Whoa look at that guy's pit stains.
Student 2: Dude those aren't pit stains, they're tit stains.
by D.Swan December 17, 2008
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the moist line a fat girl gets between her gut and tits when she sweats. this usually occurs on a hot day. extremely noticable when a bigger girl wears a smaller shirt.
dang...you know its hot out when the big'ns have tit stains.
by heatmat August 31, 2006
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