Ninchin Share definition Flag Description of a person who has a divoted chin. Name derived from the crossing of 'ninja foot' and 'chin'. See also "Grenade Chin". Matty has a ninchin, you could hide a roll of dimes up in that bitch! Ninchin by ketelred February 11, 2009 0 0 Get merch Get the Ninchin mug. Buy Now — $32.95 See more merch