Source : Webster's Revised Unabridged Dictionary (1913)

Blunder \Blun"der\, n.
   1. Confusion; disturbance. [Obs.]

   2. A gross error or mistake, resulting from carelessness,
      stupidity, or culpable ignorance.

   Syn: {Blunder}, {Error}, {Mistake}, {Bull}.

   Usage: An error is a departure or deviation from that which
          is right or correct; as, an error of the press; an
          error of judgment. A mistake is the interchange or
          taking of one thing for another, through haste,
          inadvertence, etc.; as, a careless mistake. A blunder
          is a mistake or error of a gross kind. It supposes a
          person to flounder on in his course, from
          carelessness, ignorance, or stupidity. A bull is a
          verbal blunder containing a laughable incongruity of
          ideas.

Blunder \Blun"der\, v. i. [imp. & p. p. {Blundered}; p. pr. &
   vb. n. {Blundering}.] [OE. blunderen, blondren, to stir,
   confuse, blunder; perh. allied to blend to mix, to confound
   by mixture.]
   1. To make a gross error or mistake; as, to blunder in
      writing or preparing a medical prescription. --Swift.

   2. To move in an awkward, clumsy manner; to flounder and
      stumble.

            I was never distinguished for address, and have
            often even blundered in making my bow. --Goldsmith.

            Yet knows not how to find the uncertain place, And
            blunders on, and staggers every pace. --Dryden.

   {To blunder on}.
      (a) To continue blundering.
      (b) 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.

Blunder \Blun"der\, v. t.
   1. To cause to blunder. [Obs.] ``To blunder an adversary.''
      --Ditton.

   2. To do or treat in a blundering manner; to confuse.

            He blunders and confounds all these together.
                                                  --Stillingfleet.

Source : WordNet®

blunder
     n : an embarrassing mistake [syn: {blooper}, {bloomer}, {bungle},
          {foul-up}, {fuckup}, {flub}, {botch}, {boner}, {boo-boo}]

blunder
     v 1: commit a faux pas or a fault or make a serious mistake; "I
          blundered during the job interview" [syn: {sin}, {boob},
           {goof}]
     2: make one's way clumsily or blindly; "He fumbled towards the
        door" [syn: {fumble}]
     3: utter impulsively; "He blurted out the secret"; "He
        blundered his stupid ideas" [syn: {blurt out}, {blurt}, {blunder
        out}, {ejaculate}]