Source : Webster's Revised Unabridged Dictionary (1913)

Sustain \Sus*tain"\, v. t. [imp. & p. p. {Sustained}; p. pr. &
   vb. n. {Sustaining}.] [OE. sustenen, susteinen, OF. sustenir,
   sostenir, F. soutenir (the French prefix is properly fr. L.
   subtus below, fr. sub under), L. sustinere; pref. sus- (see
   {Sub-}) + tenere to hold. See {Tenable}, and cf.
   {Sustenance}.]
   1. To keep from falling; to bear; to uphold; to support; as,
      a foundation sustains the superstructure; a beast sustains
      a load; a rope sustains a weight.

            Every pillar the temple to sustain.   --Chaucer.

   2. Hence, to keep from sinking, as in despondence, or the
      like; to support.

            No comfortable expectations of another life to
            sustain him under the evils in this world.
                                                  --Tillotson.

   3. To maintain; to keep alive; to support; to subsist; to
      nourish; as, provisions to sustain an army.

   4. To aid, comfort, or relieve; to vindicate. --Shak.

            His sons, who seek the tyrant to sustain. --Dryden.

   5. To endure without failing or yielding; to bear up under;
      as, to sustain defeat and disappointment.

   6. To suffer; to bear; to undergo.

            Shall Turnus, then, such endless toil sustain?
                                                  --Dryden.

            You shall sustain more new disgraces. --Shak.

   7. To allow the prosecution of; to admit as valid; to
      sanction; to continue; not to dismiss or abate; as, the
      court sustained the action or suit.

   8. To prove; to establish by evidence; to corroborate or
      confirm; to be conclusive of; as, to sustain a charge, an
      accusation, or a proposition.

   Syn: To support; uphold; subsist; assist; relieve; suffer;
        undergo.

Sustain \Sus*tain"\, n.
   One who, or that which, upholds or sustains; a sustainer.
   [Obs.]

         I waked again, for my sustain was the Lord. --Milton.

Source : WordNet®

sustain
     v 1: lengthen or extend in duration or space; "We sustained the
          diplomatic negociations as long as possible"; "prolong
          the treatment of the patient"; "keep up the good work"
          [syn: {prolong}, {keep up}]
     2: undergo (as of injuries and illnesses); "She suffered a
        fracture in the accident"; "He had an insulin shock after
        eating three candy bars"; "She got a bruise on her leg";
        "He got his arm broken in the scuffle" [syn: {suffer}, {have},
         {get}]
     3: provide with nourishment; "We sustained ourselves on bread
        and water"; "This kind of food is not nourishing for young
        children" [syn: {nourish}, {nurture}]
     4: supply with necessities and support; "She alone sustained
        her family"; "The money will sustain our good cause";
        "There's little to earn and many to keep" [syn: {keep}, {maintain}]
     5: be the physical support of; carry the weight of; "The beam
        holds up the roof"; "He supported me with one hand while I
        balanced on the beam"; "What's holding that mirror?" [syn:
         {hold}, {support}, {hold up}]
     6: admit as valid; "The court sustained the motion"
     7: establish or strengthen as with new evidence or facts; "his
        story confirmed my doubts"; "The evidence supports the
        defendant" [syn: {confirm}, {corroborate}, {substantiate},
         {support}, {affirm}] [ant: {negate}]