/ Dictionary / Index J jackknife-fish: Meaning and Definition of Find definitions for: jack•knife-fish Pronunciation: ( jak'nīf"fish"), [key] — pl. -fish•es, -fish. a black and white, American drum, Equetus lanceolatus, found in tropical areas of the Atlantic Ocean, having an elongated dorsal fin that is held erect. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: jackknife-fish (Thesaurus) jackknife clam jack ladder Related Content Daily Word Quiz: secular Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language