blunder

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A mistake typically caused by ignorance or carelessness.
• intransitive verb To make a mistake.
• intransitive verb To move clumsily or haltingly.
• intransitive verb To make a mistake in; botch.
• intransitive verb To utter (something) stupidly or thoughtlessly.

from The Century Dictionary.

• noun A mistake made through precipitance or mental confusion; a gross or stupid mistake.
• noun Synonyms Error, Mistake, Blunder, Bull. An error is a wandering from truth, primarily in impression, judgment, or calculation, and, by extension of the idea, in conduct; it may be a state. A mistake is a false judgment or choice; it does not, as error sometimes does, imply moral obliquity, the defect being placed wholly in the wisdom of the actor, and in its treatment of this defect the word is altogether gentle. Blunder is a strong word for a mistake which is stupid, a gross error in action or speech. A bull is a blunder in language, involving generally a very obvious and comical contradiction; but the word is sometimes applied to any particularly inapt or ludicrously inappropriate remark.
• To move or act blindly, stupidly, or without direction or steady guidance; flounder; stumble: frequently with on or along.
• To make a gross mistake, especially through mental confusion; err widely or stupidly.
• To mix (things) confusedly; confuse.
• To confound; confuse; distract; cause to make blunders: as, “to blunder an adversary,”
• To injure or destroy by blundering; mismanage: as, “to darken or blunder the cause,”
• To do or make faultily or erroneously; make mistakes in through ignorance or stupidity; bungle.
• To utter thoughtlessly or in a blundering manner; blurt out: generally with out: as, to blunder out an excuse.

from the GNU version of the Collaborative International Dictionary of English.

• intransitive verb To make a gross error or mistake.
• intransitive verb To move in an awkward, clumsy manner; to flounder and stumble.
• intransitive verb To find or reach as if by an accident involving more or less stupidity, -- applied to something desirable; as, to blunder on a useful discovery.
• transitive verb obsolete To cause to blunder.
• transitive verb To do or treat in a blundering manner; to confuse.
• noun obsolete Confusion; disturbance.
• noun A gross error or mistake, resulting from carelessness, stupidity, or culpable ignorance.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A clumsy or embarrassing mistake.
• verb To make a stupid mistake.
• verb To move blindly or clumsily.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• verb make one's way clumsily or blindly
• verb commit a faux pas or a fault or make a serious mistake
• verb utter impulsively
• noun an embarrassing mistake