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]