The Collaborative International Dictionary of English v.0.48:

Unilateral \U`ni*lat"er*al\, a. [Uni- + lateral: cf. F.
   unilat['e]ral.]
   1. Being on one side only; affecting but one side; one-sided.
      [1913 Webster]

   2. (Biol.) Pertaining to one side; one-sided; as, a
      unilateral raceme, in which the flowers grow only on one
      side of a common axis, or are all turned to one side.
      [1913 Webster]

   Unilateral contract (Law), a contract or engagement
      requiring future action only by one party.
      [1913 Webster]

WordNet (r) 3.0 (2006):

unilateral
    adj 1: involving only one part or side; "unilateral paralysis";
           "a unilateral decision" [syn: unilateral, one-sided]
           [ant: many-sided, multilateral]
    2: tracing descent from either the paternal or the maternal line
       only

Moby Thesaurus II by Grady Ward, 1.0:

48 Moby Thesaurus words for "unilateral":
   bifacial, bilateral, dihedral, flanked, handed, lateral,
   many-sided, monadal, monadic, multilateral, one-piece, one-sided,
   polyhedral, quadrilateral, sided, tetrahedral, three-sided,
   trihedral, trilateral, triquetrous, two-sided, uniangulate,
   unibivalent, unibranchiate, unicameral, unicellular, unicuspid,
   unidentate, unidigitate, unidimensional, unidirectional,
   uniflorous, unifoliate, unifoliolate, unigenital, uniglobular,
   unilinear, uniliteral, unilobed, unilobular, unimodular,
   unimolecular, uniocular, unipart, unipartite, unipolar, univalent,
   univocal