ISIANMTU Share definition Flag An acronym coined by humorist Dave Barry: I Swear I Am Not Making This Up. Commonly used when relating a story that sounds unbelievable. ONLY used when the story actually is true. Did you hear that Skinny jeans may lead to 'twisted testicles'? ISIANMTU! ISIANMTU by DeskDiva July 19, 2012 0 0 Get merch Get the ISIANMTU mug. Buy Now — $32.95 See more merch
