The Collaborative International Dictionary of English v.0.48:

blast off \blast" off\ v. i.
   to begin ascending from the ground under rocket power; -- of
   a rocket.
   [PJC]

WordNet (r) 3.0 (2006):

blast off
    v 1: launch with great force; "the rockets were blasted off"

Moby Thesaurus II by Grady Ward, 1.0:

75 Moby Thesaurus words for "blast off":
   A, alpha, altitude peak, automatic control, begin, beginning,
   blast away, burn, burnout, ceiling, commence, commencement,
   creation, cutting edge, dawn, descent, dive in, edge,
   end of burning, establishment, fall to, fire, flight, flying start,
   foundation, fresh start, get to, go ahead, head into, ignition,
   impact, institution, jump off, jump-off, kick off, kick-off,
   launch, leading edge, lift-off, new departure, oncoming, onset,
   opening, origin, origination, outbreak, outset, pitch in,
   plunge into, project, rocket launching, running start, send off,
   send-off, set about, set in, set out, set sail, set to,
   setting in motion, setting-up, shoot, shot, square one, start,
   start in, start off, start out, start-off, starting point,
   take off, take-off, trajectory, turn to, velocity peak