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.

Source: Webster's Revised Unabridged Dictionary (1913)