The Collaborative International Dictionary of English v.0.48:

Brickbat \Brick"bat`\, n.
   A piece or fragment of a brick. See 1st Bat, n. 4. --Bacon.
   [1913 Webster]

WordNet (r) 3.0 (2006):

brickbat
    n 1: a fragment of brick used as a weapon
    2: blunt criticism

Moby Thesaurus II by Grady Ward, 1.0:

41 Moby Thesaurus words for "brickbat":
   Irish confetti, affront, aspersion, atrocity, bola, bolt,
   boomerang, contempt, contumely, countermissile, cut, despite, dump,
   enormity, flout, flouting, gibe, humiliation, indignity, injury,
   insult, jeer, jeering, missile, mock, mockery, offense, outrage,
   projectile, put-down, rock, rocket, scoff, scurrility, stone,
   taunt, throw stick, throwing-stick, torpedo,
   uncomplimentary remark, waddy