Source : Webster's Revised Unabridged Dictionary (1913)

Subsistence \Sub*sist"ence\, n. [Cf. F. subsistance, L.
   subsistentia.]
   1. Real being; existence.

            Not only the things had subsistence, but the very
            images were of some creatures existing.
                                                  --Stillingfleet.

   2. Inherency; as, the subsistence of qualities in bodies.

   3. That which furnishes support to animal life; means of
      support; provisions, or that which produces provisions;
      livelihood; as, a meager subsistence.

            His viceroy could only propose to himself a
            comfortable subsistence out of the plunder of his
            province.                             --Addison.

   4. (Theol.) Same as {Hypostasis}, 2. --Hooker.

Source : WordNet®

subsistence
     n 1: minimal (or marginal) resources for subsisting; "social
          security provided only a bare subsistence"
     2: a means of surviving; "farming is a hard means of
        subsistence"
     3: the state of existing in reality; having substance