WordNet (r) 3.0 (2006):

speedup
    n 1: the act of accelerating; increasing the speed [syn:
         acceleration, quickening, speedup] [ant:
         deceleration]

Moby Thesaurus II by Grady Ward, 1.0:

31 Moby Thesaurus words for "speedup":
   accelerando, acceleration, aggravation, beefing-up, blowing up,
   blowup, concentration, condensation, consolidation, deepening,
   drive, enhancement, exacerbation, exaggeration, explosion, getaway,
   heating-up, heightening, impetus, information explosion,
   intensification, magnification, pickup, population explosion,
   quickening, redoubling, reinforcement, step-up, strengthening,
   thrust, tightening