The Collaborative International Dictionary of English v.0.48:

Prepossess \Pre`pos*sess"\, v. t. [imp. & p. p. Prepossessed;
   p. pr. & vb. n. Prepossessing.]
   [1913 Webster]
   1. To preoccupy, as ground or land; to take previous
      possession of. --Dryden.
      [1913 Webster]

   2. To preoccupy, as the mind or heart, so as to preclude
      other things; hence, to bias or prejudice; to give a
      previous inclination to, for or against anything; esp., to
      induce a favorable opinion beforehand, or at the outset.
      [1913 Webster]

            It created him enemies, and prepossessed the lord
            general.                              --Evelyn.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Prepossessing \Pre`pos*sess"ing\, a.
   Tending to invite favor; attracting confidence, favor,
   esteem, or love; attractive; as, a prepossessing manner. --
   Pre`pos*sess"ing*ly, adv.
   [1913 Webster]

WordNet (r) 3.0 (2006):

prepossessing
    adj 1: creating a favorable impression; "strong and vigorous and
           of prepossessing appearance"

Moby Thesaurus II by Grady Ward, 1.0:

70 Moby Thesaurus words for "prepossessing":
   alluring, appealing, appetizing, attracting, attractive, beautiful,
   beguiling, bewitching, blandishing, cajoling, captivating,
   catching, charismatic, charming, coaxing, come-hither, coquettish,
   delightful, drawing, enchanting, engaging, enravishing,
   enthralling, enticing, entrancing, exciting, exotic, exquisite,
   fascinating, favorable, fetching, flirtatious, glamorous,
   good-looking, handsome, heart-robbing, hypnotic, interesting,
   intriguing, inviting, irresistible, lovely, luxurious, magnetic,
   mesmeric, mouth-watering, piquant, pleasing, provocative,
   provoquant, ravishing, seducing, seductive, sensuous, siren,
   sirenic, spellbinding, spellful, taking, tantalizing, teasing,
   tempting, thrilling, tickling, titillating, titillative,
   voluptuous, winning, winsome, witching