The Collaborative International Dictionary of English v.0.48:

half-baked \half-baked\ a.
   1. Insufficiently or poorly planned or thought out;
      impractical or unrealistic; as, a half-baked proposal;
      half-baked ideas; -- of plans, theories, proposals, etc.
      [PJC]

   2. Insufficiently cooked; -- of food.
      [PJC]

WordNet (r) 3.0 (2006):

half-baked
    adj 1: foolish; totally unsound; "a crazy scheme"; "half-baked
           ideas"; "a screwball proposal without a prayer of
           working" [syn: crazy, half-baked, screwball,
           softheaded]
    2: insufficiently cooked [syn: half-baked, underdone]