Source : Webster's Revised Unabridged Dictionary (1913)

Spectral \Spec"tral\, a.
   1. Of or pertaining to a specter; ghosty.

            He that feels timid at the spectral form of evil is
            not the man to spread light.          --F. W.
                                                  Robertson.

   2. (Opt.) Of or pertaining to the spectrum; made by the
      spectrum; as, spectral colors; spectral analysis.

   {Spectral lemur}. (Zo["o]l.) See {Tarsius}.