The Collaborative International Dictionary of English v.0.48:

Subsist \Sub*sist"\, v. i. [imp. & p. p. Subsisted; p. pr. &
   vb. n. Subsisting.] [L. subsistere to stand still, stay,
   remain alive; sub under + sistere to stand, to cause to
   stand, from stare to stand: cf. F. subsister. See Stand.]
   1. To be; to have existence; to inhere.
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            And makes what happiness we justly call,
            Subsist not in the good of one, but all. --Pope.
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   2. To continue; to retain a certain state.
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            Firm we subsist, yet possible to swerve. --Milton.
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   3. To be maintained with food and clothing; to be supported;
      to live. --Milton.
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            To subsist on other men's charity.    --Atterbury.
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The Collaborative International Dictionary of English v.0.48:

Subsist \Sub*sist"\, v. t.
   To support with provisions; to feed; to maintain; as, to
   subsist one's family.
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         He laid waste the adjacent country in order to render
         it more difficult for the enemy to subsist their army.
                                                  --Robertson.
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WordNet (r) 3.0 (2006):

subsist
    v 1: support oneself; "he could barely exist on such a low
         wage"; "Can you live on $2000 a month in New York City?";
         "Many people in the world have to subsist on $1 a day"
         [syn: exist, survive, live, subsist]

Moby Thesaurus II by Grady Ward, 1.0:

73 Moby Thesaurus words for "subsist":
   abide, be, be alive, be animate, be extant, be found,
   be in existence, be left, be met with, be present, be the case,
   be there, bide, breathe, carry on, continue, continue to be, cope,
   defeat time, defy time, draw breath, dwell, eke out, endure, exist,
   extend, fetch breath, get by, go on, happen to be, have being,
   have life, have place, hold, hold on, hold out, keep, keep afloat,
   keep on, last, last long, last out, live, live and breathe,
   live on, live through, maintain, make ends meet, make out, manage,
   move, obtain, occur, perdure, perennate, persist, prevail, remain,
   respire, rest, run, run on, scrape along, stand, stay, stay on,
   survive, sustain, tarry, tide over, walk the earth, wear,
   wear well