The Collaborative International Dictionary of English v.0.48:

Exist \Ex*ist"\, v. i. [imp. & p. p. Existed; p. pr. & vb. n.
   Existing.] [L. existere, exsistere, to step out or forth,
   emerge, appear, exist; ex out + sistere to cause to stand, to
   set, put, place, stand still, fr. stare to stand: cf. F.
   exister. See Stand.]
   1. To be as a fact and not as a mode; to have an actual or
      real being, whether material or spiritual.
      [1913 Webster]

            Who now, alas! no more is missed
            Than if he never did exist.           --Swift.
      [1913 Webster]

            To conceive the world . . . to have existed from
            eternity.                             --South.
      [1913 Webster]

   2. To be manifest in any manner; to continue to be; as, great
      evils existed in his reign.
      [1913 Webster]

   3. To live; to have life or the functions of vitality; as,
      men can not exist in water, nor fishes on land.

   Syn: See Be.
        [1913 Webster]

WordNet (r) 3.0 (2006):

exist
    v 1: have an existence, be extant; "Is there a God?" [syn:
         exist, be]
    2: 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]