The Collaborative International Dictionary of English v.0.48:

Misstep \Mis*step"\, n.
   A wrong step; an error of conduct.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Misstep \Mis*step"\, v. i.
   To take a wrong step; to go astray.
   [1913 Webster]

WordNet (r) 3.0 (2006):

misstep
    n 1: an unintentional but embarrassing blunder; "he recited the
         whole poem without a single trip"; "he arranged his robes
         to avoid a trip-up later"; "confusion caused his
         unfortunate misstep" [syn: trip, trip-up, stumble,
         misstep]

Moby Thesaurus II by Grady Ward, 1.0:

28 Moby Thesaurus words for "misstep":
   balk, bevue, bloomer, blooper, blunder, error, false move,
   false step, faux pas, gaffe, goof, howler, inadvertence,
   inadvertency, indiscretion, lapse, lapsus calami, lapsus linguae,
   loose thread, miscue, mistake, omission, oversight, slip, slipup,
   stumble, trip, wrong step