(1):

(n.) A word having but one meaning.

(2):

(n.) A generic term, or a term applicable in the same sense to all the species it embraces.

(3):

(n.) Having always the same drift or tenor; uniform; certain; regular.

(4):

(n.) Unequivocal; indubitable.

(5):

(a.) Having unison of sound, as the octave in music. See Unison, n., 2.

(6):

(a.) Having one meaning only; - contrasted with equivocal.