A Gilseth is when you pop a boner so hard that you can't get it to go back down. after a while the Gilseth get so hard it cuts off circulation to your balls turning them blue. You generally get these when you see a really hot chick or in some cases a guy if your gay or a transvestite.

(noun) A successful type of theft which results in an acceptable, impressive and rewarding payday for the protagonist.