Gilthy Share definition Flag When an elderly person (presumably a grandparent) does something particularly filthy or savage. Did you see that guy at the old folks' home just grab the nurse's ass when she bent down to put his shoes on? That's a gilthy move right there. Gilthy by Sensei Chang September 12, 2017 0 0 Get merch Get the Gilthy mug. Buy Now — $32.95 See more merch