The Collaborative International Dictionary of English v.0.48:

Bombardment \Bom*bard"ment\, n. [F. bombardement.]
   An attack upon a fortress or fortified town, with shells, hot
   shot, rockets, etc.; the act of throwing bombs and shot into
   a town or fortified place.
   [1913 Webster] Bombardo

WordNet (r) 3.0 (2006):

bombardment
    n 1: the rapid and continuous delivery of linguistic
         communication (spoken or written); "a barrage of
         questions"; "a bombardment of mail complaining about his
         mistake" [syn: barrage, bombardment, outpouring,
         onslaught]
    2: the heavy fire of artillery to saturate an area rather than
       hit a specific target; "they laid down a barrage in front of
       the advancing troops"; "the shelling went on for hours
       without pausing" [syn: barrage, barrage fire, battery,
       bombardment, shelling]
    3: the act (or an instance) of subjecting a body or substance to
       the impact of high-energy particles (as electrons or alpha
       rays)
    4: an attack by dropping bombs [syn: bombing, bombardment]

Moby Thesaurus II by Grady Ward, 1.0:

46 Moby Thesaurus words for "bombardment":
   air raid, alpha decay, atom-chipping, atom-smashing,
   atomic disintegration, atomic reaction, atomization, beta decay,
   blitz, blitzkrieg, breeding, broadside, bullet, burst, cannonade,
   chain reaction, cleavage, disintegration series, dissociation,
   drumfire, exchange reaction, fission, fission reaction, fusillade,
   gamma decay, hail, ionization, lightning attack, lightning war,
   neutron reaction, nonreversible reaction, nuclear fission,
   nucleization, photodisintegration, proton gun, proton reaction,
   reversible reaction, salvo, shower, splitting the atom,
   stimulation, strafe, strafing, target, thermonuclear reaction,
   volley