Source : Webster's Revised Unabridged Dictionary (1913)

Auburn \Au"burn\, a. [OE. auburne blonde, OF. alborne, auborne,
   fr. LL. alburnus whitish, fr. L. albus white. Cf. {Alburn}.]
   1. Flaxen-colored. [Obs.] --Florio.

   2. Reddish brown.

            His auburn locks on either shoulder flowed.
                                                  --Dryden.

Source : WordNet®

auburn
     adj : (of hair) colored a moderate brown; "auburn hair" [syn: {reddish-brown}]