blun·der / ˈbləndər/ • n. a stupid or careless mistake.• v. [intr.] make such a mistake; act or speak clumsily: the mayor and the City Council have blundered in an ill-advised campaign. ∎  move clumsily or as if unable to see: we were blundering around in the darkness.DERIVATIVES: blun·der·er n.blun·der·ing·ly adv.

blunder move blindly or stupidly XIV; make a stupid mistake XVIII. prob. of Scand. orig.; cf. MSw., Norw. blundra shut the eyes, frequent, of the base found in ON. blunda, rel. to BLIND; but the sense-development is not clear.