a. 1. Of or pertaining to a specter; ghosty. [ 1913 Webster ]
He that feels timid at the spectral form of evil is not the man to spread light. F. W. Robertson. [ 1913 Webster ]
2. (Opt.) Of or pertaining to the spectrum; made by the spectrum; as, spectral colors; spectral analysis. [ 1913 Webster ]
Spectral lemur. (Zool.) See Tarsius. [ 1913 Webster ]
adv. In the form or manner of a specter. [ 1913 Webster ]