Gatisimo Share definition Flag A lot of cat. A very large, often obese cat. Comes from the spanish word Gato and the superlative isimo. Fat bastard is one large cat, he's a frickin' gatisimo Gatisimo by Jack the King August 1, 2008 0 0 Get merch Get the Gatisimo mug. Buy Now — $32.95 See more merch