Source : Webster's Revised Unabridged Dictionary (1913)

Bilateral \Bi*lat"er*al\, a. [Pref. bi- + lateral: cf. F.
   bilat['e]ral.]
   1. Having two sides; arranged upon two sides; affecting two
      sides or two parties.

   2. (Biol.) Of or pertaining to the two sides of a central
      area or organ, or of a central axis; as, bilateral
      symmetry in animals, where there is a similarity of parts
      on the right and left sides of the body.

Source : WordNet®

bilateral
     adj 1: having identical parts on each side of an axis [syn: {isobilateral},
             {bilaterally symmetrical}, {bilaterally symmetric}]
     2: having two sides or parts [syn: {two-sided}] [ant: {unilateral},
         {multilateral}]
     3: affecting or undertaken by two parties; "a bilateral
        agreement between the United States and Japan"