/ Dictionary / Index S sustainer: Meaning and Definition of Find definitions for: sus•tain•er Pronunciation: (su-stā'nur), [key] — n. a person or thing that sustains. any stage of a multistage rocket or guided missile that sustains flight after the burnout of the booster. the rocket engine or cluster of engines contained in such a stage. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: sustainer (Thesaurus) sustained-release sustaining program 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