The Collaborative International Dictionary of English v.0.48:

Extant \Ex"tant\, a. [L. extans, -antis, or exstans, -antis, p.
   pr. of extare, exstare, to stand out or forth; ex out + stare
   to stand: cf. F. extant. See Stand.]
   1. Standing out or above any surface; protruded.
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            That part of the teeth which is extant above the
            gums.                                 --Ray.
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            A body partly immersed in a fluid and partly extant.
                                                  --Bentley.
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   2. Still existing; not destroyed or lost; outstanding.
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            Writings that were extant at that time. --Sir M.
                                                  Hale.
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            The extant portraits of this great man. --I. Taylor.
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   3. Publicly known; conspicuous. [Obs.] --B. Jonson.
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WordNet (r) 3.0 (2006):

extant
    adj 1: still in existence; not extinct or destroyed or lost;
           "extant manuscripts"; "specimens of graphic art found
           among extant barbaric folk"- Edward Clodd [ant:
           extinct, nonextant]

Moby Thesaurus II by Grady Ward, 1.0:

37 Moby Thesaurus words for "extant":
   actual, alive, around, as is, being, contemporaneous, contemporary,
   current, existent, existing, fresh, immanent, immediate, in being,
   in effect, in existence, in force, instant, latest, living, modern,
   new, on foot, present, present-age, present-day, present-time,
   prevalent, running, subsistent, subsisting, that be, that is,
   topical, under the sun, up-to-date, up-to-the-minute