schmo Share definition Flag Yiddish for an idiot or a cuckold. Essential loan word in New Yorkese English, along with all the other Yiddish insults. See also schmuck. That schmo just took my spot and flipped me the bird. Jerk. schmo by ignor July 5, 2003 0 0 Get merch Get the schmo mug. Buy Now — $32.95 See more merch