No longer in existence; lost or especially having died out leaving no living representatives:
— An extinct species of fish.
— An extinct royal family.
— Extinct laws and customs.

synonym: nonextant.

Roget 2: inexistent^†, nonexistent etc. 1; negative, blank; missing, omitted; absent etc. 187; insubstantial, shadowy, spectral, visionary.    unreal, potential, virtual; baseless, in nubibus [Lat.]; unsubstantial etc. 4; vain.    unborn, uncreated^†, unbegotten, unconceived, unproduced, unmade.    perished, annihilated, etc. v.; extinct, exhausted, gone, lost, vanished, departed, gone with the wind; defunct etc. (dead) 360.    fabulous, ideal etc. (imaginary) 515, supposititious etc. 514.    ... show more

Roget 122: past, gone, gone by, over, passed away, bygone, foregone; elapsed, lapsed, preterlapsed^†, expired, no more, run out, blown over, has-been, that has been, extinct, antediluvian, antebellum, never to return, gone with the wind, exploded, forgotten, irrecoverable; obsolete etc. (old) 124.    former, pristine, quondam, ci-devant [Fr.], late; ancestral.    foregoing; last, latter; recent, over night; preterperfect^†, preterpluperfect^†.    looking back etc. v.; retrospective, retroactive; archaeological etc. n.. ... show more

Roget 162: destroyed etc. v.; perishing etc. v.; trembling to its fall, nodding to its fall, tottering to its fall; in course of destruction etc. n.; extinct.    all-destroying, all-devouring, all-engulfing.    destructive, subversive, ruinous, devastating; incendiary, deletory^†; destroying etc. n.. suicidal; deadly etc. (killing) 361.    ... show more

Roget 360: dead, lifeless; deceased, demised, departed, defunct, extinct; late, gone, no more; exanimate^†, inanimate; out of the world, taken off, released; departed this life etc. v.; dead and gone; dead as a doornail, dead as a doorpost^†, dead as a mutton, dead as a herring, dead as nits; launched into eternity, gone to one's eternal reward, gone to meet one's maker, pushing up daisies, gathered to one's fathers, numbered with the dead.    dying etc. v.; moribund, morient^†; hippocratic; in articulo, in extremis; in the jaws of death, in the agony of death; going off; aux abois [Fr.]; one one's last legs, on one's death bed; at the point of death, at death's door, at the last gasp; near one's end, given over, booked; with one foot in the grave, tottering on the brink of the grave.    stillborn; mortuary; deadly etc. (killing) 361.    ... show more

of e.g. volcanos Permanently inactive.

Being out or having grown cold:
— Threw his extinct cigarette into the stream.

synonym: out.