blun·der 
(blŭndər)
(blŭndər)n.
A mistake typically caused by ignorance or carelessness.
v. blun·dered, blun·der·ing, blun·ders
v.intr.
1. To make a mistake.
2. To move clumsily or haltingly.
v.tr.
1. To make a mistake in; botch: would-be thieves blundering a break-in.
2. To utter (something) stupidly or thoughtlessly.
[From Middle English blunderen, to go blindly, perhaps from Old Swedish blundra, have one's eyes closed, from Old Norse blunda.]
blunder·er n.
blunder·ing·ly adv.
Synonyms: blunder, bumble1, flounder1, lumber2, lurch1, stagger, stumble, totter
These verbs mean to move awkwardly or unsteadily: blundered about the dark room; bumbled in the door and knocked over a chair; floundered up the muddy path; an elephant lumbering along a trail; twisted her ankle and lurched home; staggered under the heavy weight; stumbled down the hall in a stupor; tottered across the finish line in exhaustion.
These verbs mean to move awkwardly or unsteadily: blundered about the dark room; bumbled in the door and knocked over a chair; floundered up the muddy path; an elephant lumbering along a trail; twisted her ankle and lurched home; staggered under the heavy weight; stumbled down the hall in a stupor; tottered across the finish line in exhaustion.