THESAURUS
ad-lib, caught napping, caught off balance, caught short, extemporaneous, extemporized, haphazard, hasty, impromptu, improvised, makeshift, precipitate, rough-and-ready, snap, surprised, taken aback, taken by surprise, taken unawares, tripped up, unarranged, unbegotten, unbegun, unborn, unconceived, unconcocted, uncontrived, uncreated, undeliberated, undevised, unhatched, unmanufactured, unorganized, unplanned, unpremeditated, unprepared, unprimed, unproduced, unready, unstudied
ROGET THESAURUS
Inexistence
N
inexistence, nonexistence, nonsubsistence, nonentity, nil, negativeness, nullity, nihility, nihilism, tabula rasa, blank, abeyance, absence, no such thing, nonbeing, nothingness, oblivion, annihilation, extinction, extinguishment, extirpation, Nirvana, obliteration, inexistent, nonexistent, negative, blank, missing, omitted, absent, insubstantial, shadowy, spectral, visionary, unreal, potential, virtual, baseless, in nubibus, unsubstantial, vain, unborn, uncreated, unbegotten, unconceived, unproduced,
unmade, perished, annihilated extinct, exhausted, gone, lost, vanished, departed, gone with the wind, defunct, fabulous, ideal, supposititious &c, negatively, virtually, non ens.