(grammar) an adjective used as a noun (sensu stricto); an absolute adjective (nominalized adjective).
(grammar, dated) an adjective
3. An adjective or adnoun, expresses a particular quality ascribed to a substantive—A good man, a bad man, a studious man, a lazy man—The words good, bad, studious, and lazy, express the particular quality which belong to such or such a man.