A triumphant knee banger is when you push a girl's head towards your nether regions in hopes of getting a blowie, but you accidentally slam her head against your knee. She then vomits and grosses you out, the toxic waste falls on your crotch, staining your pants with vomit. After a while you realise that it doesn't feel so bad and cum. Hence the name.
by thighmaster69 October 28, 2018
Get the Triumphant Knee Bangermug.