The Collaborative International Dictionary of English v.0.48:

Bearish \Bear"ish\, a.
   1. Partaking of the qualities of a bear; resembling a bear in
      temper or manners. --Harris.
      [1913 Webster]

   2. (Stock market) Fearful of or anticipating falling prices,
      as in the stock market; as, bearish sentiment inhibited
      buying.
      [PJC]

   3. (Stock market) Tending to cause prices to fall. "bearish
      news about inflation caused a sharp drop in the Dow."
      [PJC]

   4. Hence: Pessimistic.
      [PJC]

WordNet (r) 3.0 (2006):

bearish
    adj 1: expecting prices to fall

Moby Thesaurus II by Grady Ward, 1.0:

49 Moby Thesaurus words for "bearish":
   abrupt, aggressive, beastly, bitchy, bluff, blunt, brash, brusque,
   cankered, cantankerous, cavalier, churlish, crabbed, cranky, cross,
   cross-grained, crotchety, crusty, curt, cussed, disagreeable,
   excitable, feisty, fractious, gruff, harsh, huffish, huffy,
   irascible, irritable, mean, ornery, perverse, rough, severe, sharp,
   short, snappish, snippy, spiteful, spleeny, splenetic, surly,
   testy, truculent, ugly, vinegarish, vinegary, waspish