Source : Webster's Revised Unabridged Dictionary (1913)

Soluble \Sol"u*ble\, a. [L. solubilis, fr. solvere, solutum, to
   loosen, to dissolve: cf. F. soluble. See {Solve}, and cf.
   {Solvable}.]
   1. Susceptible of being dissolved in a fluid; capable of
      solution; as, some substances are soluble in alcohol which
      are not soluble in water.

            Sugar is . . . soluble in water and fusible in fire.
                                                  --Arbuthnot.

   2. Susceptible of being solved; as, a soluble algebraic
      problem; susceptible of being disentangled, unraveled, or
      explained; as, the mystery is perhaps soluble. ``More
      soluble is this knot.'' --Tennyson.

   3. Relaxed; open or readily opened. [R.] ``The bowels must be
      kept soluble.'' --Dunglison.

   {Soluble glass}. (Chem.) See under {Glass}.

Source : WordNet®

soluble
     adj 1: (of a substance) capable of being dissolved in some solvent
            (usually water) [ant: {insoluble}]
     2: susceptible of solution or of being solved or explained;
        "the puzzle is soluble" [ant: {insoluble}]