WordNet (r) 3.0 (2006):

step on it
    v 1: move fast; "He rushed down the hall to receive his guests";
         "The cars raced down the street" [syn: rush, hotfoot,
         hasten, hie, speed, race, pelt along, rush
         along, cannonball along, bucket along, belt along,
         step on it] [ant: dawdle, linger]

Moby Thesaurus II by Grady Ward, 1.0:

45 Moby Thesaurus words for "step on it":
   accelerate, bolt, career, crack on, dart, dash, fling, gain ground,
   get cracking, haste, hasten, hie, hop to it, hotfoot, hump,
   hump it, hurry, hurry up, hurtle, make haste, open the throttle,
   pick up speed, post, put on, put on steam, quicken, race, rev,
   rush, scamper, scoot, scour, scramble, scud, scurry, scuttle,
   shag ass, shake it up, shoot, skedaddle, snap to it, speed up,
   step up, tear, tear ass