The Collaborative International Dictionary of English v.0.48:

Errant \Er"rant\, a. [F. errant, p. pr. fr. OF. errer to travel,
   LL. iterare, fr. L. iter journey; confused somewhat with L.
   errare to err. See Eyre, and cf. Arrant, Itinerant.]
   1. Wandering; deviating from an appointed course, or from a
      direct path; roving.
      [1913 Webster]

            Seven planets or errant stars in the lower orbs of
            heaven.                               --Sir T.
                                                  Browne.
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   2. Notorious; notoriously bad; downright; arrant.
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            Would make me an errant fool.         --B. Jonson.
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   3. (Eng. Law) Journeying; itinerant; -- formerly applied to
      judges who went on circuit and to bailiffs at large.
      --Mozley & W.
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The Collaborative International Dictionary of English v.0.48:

Errant \Er"rant\, n.
   One who wanders about. [Obs.] --Fuller.
   [1913 Webster]

WordNet (r) 3.0 (2006):

errant
    adj 1: straying from the right course or from accepted
           standards; "errant youngsters"
    2: uncontrolled motion that is irregular or unpredictable; "an
       errant breeze"