step-great-grandchild Share definition Flag 1. The child of one's stepgrandchild. 2. The stepchild of one's grandchild. My step-great-grandchild is a good person. step-great-grandchild by Elivaldeq November 24, 2019 0 0 Get merch Get the step-great-grandchild mug. Buy Now — $32.95 See more merch