Source : Webster's Revised Unabridged Dictionary (1913)

Accelerate \Ac*cel"er*ate\, v. t. [imp. & p. p. {Accelerated};
   p. pr. & vb. n. {Accelerating}.] [L. acceleratus, p. p. of
   accelerare; ad + celerare to hasten; celer quick. See
   {Celerity}.]
   1. To cause to move faster; to quicken the motion of; to add
      to the speed of; -- opposed to {retard}.

   2. To quicken the natural or ordinary progression or process
      of; as, to accelerate the growth of a plant, the increase
      of wealth, etc.

   3. To hasten, as the occurence of an event; as, to accelerate
      our departure.

   {Accelerated motion} (Mech.), motion with a continually
      increasing velocity.

   {Accelerating force}, the force which causes accelerated
      motion.                                     --Nichol.

   Syn: To hasten; expedite; quicken; dispatch; forward;
        advance; further.

Source : WordNet®

accelerating
     adj : increasing in speed; becoming progressively faster; "the
           accelerating inflation was cause for great concern"