/ Dictionary / Index O onomastic: Meaning and Definition of Find definitions for: on•o•mas•tic Pronunciation: (on"u-mas'tik), [key] — adj. of or pertaining to proper names. of or pertaining to onomastics. (of a signature) written in the handwriting other than that of the document, instrument, etc., to which it is appended. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: onomastic (Thesaurus) onomasiology onomasticon Related Content Daily Word Quiz: clairvoyant Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language