From 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]
From The Collaborative International Dictionary of English v.0.48:
existing \existing\ adj.
1. having existence or being or actuality; as, much of the
beluga caviar existing in the world is found in the Soviet
Union and Iran. Opposite of nonexistent. [Narrower
terms: active, alive; extant, surviving] Also See:
extant.
Syn: existent.
[WordNet 1.5]
2. Present. Opposite of absent.
[WordNet 1.5]
3. Presently existing; as, the existing system.
[WordNet 1.5]