The Collaborative International Dictionary of English v.0.48:

Brunt \Brunt\ (br[u^]nt), n. [OE. brunt, bront, fr. Icel. bruna
   to rush; cf. Icel. brenna to burn. Cf. Burn, v. t.]
   1. The heat, or utmost violence, of an onset; the strength or
      greatest fury of any contention; as, the brunt of a
      battle.
      [1913 Webster]

   2. The force of a blow; shock; collision. "And heavy brunt of
      cannon ball." --Hudibras.
      [1913 Webster]

            It is instantly and irrecoverably scattered by our
            first brunt with some real affair of common life.
                                                  --I. Taylor.
      [1913 Webster]

WordNet (r) 3.0 (2006):

brunt
    n 1: main force of a blow etc; "bore the brunt of the attack"

Moby Thesaurus II by Grady Ward, 1.0:

37 Moby Thesaurus words for "brunt":
   appulse, bulldozing, bulling, bump, burden, cannon, carambole,
   carom, clash, collision, concussion, crack-up, crash, crump,
   crunch, encounter, full force, hammering, impact, impingement,
   mauling, meeting, onslaught, onus, percussion, ramming, shock,
   sideswipe, sledgehammering, smash, smash-up, smashing, stress,
   thrusting, violence, weight, whomp