The Collaborative International Dictionary of English v.0.48:

Bludgeon \Bludg"eon\, n. [Cf. Ir. blocan a little block, Gael.
   plocan a mallet, W. plocyn, dim. of ploc block; or perh.
   connected with E. blow a stroke. Cf. Block, Blow a
   stroke.]
   A short stick, with one end loaded, or thicker and heavier
   that the other, used as an offensive weapon.
   [1913 Webster]

WordNet (r) 3.0 (2006):

bludgeon
    n 1: a club used as a weapon
    v 1: overcome or coerce as if by using a heavy club; "The
         teacher bludgeoned the students into learning the math
         formulas"
    2: strike with a club or a bludgeon [syn: club, bludgeon]

Moby Thesaurus II by Grady Ward, 1.0:

42 Moby Thesaurus words for "bludgeon":
   bat, baton, be imminent, billy, billy club, blackjack, bluster,
   bluster out of, bounce, browbeat, bulldoze, bully, bullyrag, club,
   coerce, comminate, cow, demoralize, denounce, dragoon, forebode,
   harass, hector, hijack, huff, intimidate, look threatening, lower,
   menace, nightstick, shanghai, shillelagh, steamroller, strong-arm,
   systematically terrorize, terrorize, threaten, truncheon,
   use violence, utter threats against, war club, warn