1. Noun.  (uncountable) The act of accelerating, or the state of being accelerated; increase of motion or action; as opposed to retardation or deceleration.
  2. Noun.  (countable) The amount by which a speed or velocity increases (and so a scalar quantity or a vector quantity).
  3. Noun.  (physics) The change of velocity with respect to time (can include deceleration or changing direction).

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This entry was last updated on RefTopia from its source on 3/20/2012.