cath bag Share definition Flag one that lies or exaggerates (poorly) about experiences in a pathetic attempt to seem like a bad-ass. this behavior is most common in those who follow catholic beleifs. Hoy is such a cath bag. he is white and told me that he has 10 inches. cath bag by C. Bartoe March 20, 2008 0 0 Get merch Get the cath bag mug. Buy Now — $32.95 See more merch