Source : Webster's Revised Unabridged Dictionary (1913)

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.

            Seven planets or errant stars in the lower orbs of
            heaven.                               --Sir T.
                                                  Browne.

   2. Notorious; notoriously bad; downright; arrant.

            Would make me an errant fool.         --B. Jonson.

   3. (Eng. Law) Journeying; itinerant; -- formerly applied to
      judges who went on circuit and to bailiffs at large.
      --Mozley & W.

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

Source : WordNet®

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"