Blunder n. A usually serious mistake typically caused by ignorance or confusion. v. blun·dered, blun·der·ing, blun·ders v.intr. 1. To move clumsily or blindly. 2. To make a usually serious mistake. v.tr. 1. To make a stupid, usually serious error in; botch. 2. To utter (something) stupidly or though...