yoinksies Share definition Flag Said when stealing another persons posession(s), usually in the case of food, or a seat at a party. *friend stands up to get a drink and returns, finding you in his seat* Yoinksies! You didn't call seat check. yoinksies by Stefan vW February 20, 2008 0 0 Get merch Get the yoinksies mug. Buy Now — $32.95 See more merch