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when you insert for any reason your thumb into your balloon knot, usually though to increase pleasure during masturbation, and when you are done slappin' your junk around and start to feel 1/2 homo, you pull out your sticky thumb covered in butt sweat, and shitty ass goo out and you realize you have Swamp Thumb.. you know, the funk that just doens't wash off... it's like a juicy ass coating on your tunmb that usually remains malodorous for a few hours..
So hey bro, i was jackin' my cock the other night, and right before i shot my cock-snot, i jammed my thumb up into my poopchute for a little colon tickle... when i pulled it out, i realized i had some nasty swamp thumb, so i gave my roommate a hitler while he was sleeping!
by xbhotlava October 04, 2007
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