half-niece-in-law Share definition Flag 1. The daughter-in-law of one's half-sibling. 2. The daughter of one's spouse's half-sibling. My half-niece-in-law is a good person. half-niece-in-law by Elivaldeq November 24, 2019 0 0 Get merch Get the half-niece-in-law mug. Buy Now — $32.95 See more merch