/ Dictionary / Index T threadfin: Meaning and Definition of Find definitions for: thread•fin Pronunciation: (thred'fin"), [key] — n. any spiny-rayed fishes of the family Polynemidae, having the lower part of the pectoral fin composed of numerous, separate, filamentous rays. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: threadfin (Thesaurus) thread escutcheon threadfish Related Content Daily Word Quiz: frugal Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language