/ Dictionary / Index A acceleration: Meaning and Definition of Find definitions for: ac•cel•er•a•tion Pronunciation: (ak-sel"u-rā'shun), [key] — n. the act of accelerating; increase of speed or velocity. a change in velocity. the time rate of change of velocity with respect to magnitude or direction; the derivative of velocity with respect to time. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: acceleration (Thesaurus) accelerated reader acceleration clause Related Content Daily Word Quiz: fervor Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language