balloon trunks Share definition Flag When a guy farts in a swimming pool and his swimming trunks inflate with trapped ass gas. Look at that fool in the shallow end.Like nobody is going to notice his balloon trunks floating up around his armpits. balloon trunks by wolfbait51 May 21, 2011 0 0 Get merch Get the balloon trunks mug. Buy Now — $32.95 See more merch