(Noun) In Southwestern US slang, a "gumdropper" is a man wearing old blue jeans with loose, stretched-out seams, who has seated himself on a stool in a neighborhood watering hole and tugged a small section of his scrotum out through the loose seam at the crotch of the pants, (or, alternately, through a small hole in the fabric itself). The goal of a "gumdropper" is to make others believe that he has actually dropped a wad of chewed gum into his lap, then laugh himself silly when his victims realize they have actually been staring at his shriveled ball-bag.
A typical application of the "gumdrop" scenario goes as follows: When an attractive young woman passes by a "gumdropper", he draws her attention by loudly announcing "Aw, jeez! Wouldja lookit that? I went 'n' dropped my dang bubble-gum!" The woman will instinctively look in the direction of the man's downward gaze, with her initial expression of curiosity quickly changing to one of disgust as she realizes that she's actually gotten an eye-full of his hairy, wrinkled-up nut-sac!