Source : Webster's Revised Unabridged Dictionary (1913)

Unsaturated \Un*sat"u*ra`ted\, a.
   1. Capable of absorbing or dissolving to a greater degree;
      as, an unsaturated solution.

   2. (Chem.) Capable of taking up, or of uniting with, certain
      other elements or compounds, without the elimination of
      any side product; thus, aldehyde, ethylene, and ammonia
      are unsaturated.

Source : WordNet®

unsaturated
     adj 1: not saturated; capable of dissolving more of a substance at
            a given temperature; "an unsaturated salt solution"
            [ant: {saturated}]
     2: used of a compound (especially of carbon) containing atoms
        sharing more than one valence bond; "unsaturated fats"
        [ant: {saturated}]
     3: (of color) not chromatically pure; diluted; "an unsaturated
        red" [ant: {saturated}]