/ Dictionary / Index S speed demon: Meaning and Definition of Find definitions for: speed' de"mon Pronunciation: [key] — Informal. Informal. a person who travels or works at high speed. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. speed chess speeder Related Content Daily Word Quiz: fidelity Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language