Synonyms: not possible, beyond the bounds of possibility, out of the question, not worth considering, unattainable, unachievable, unobtainable, hopeless, impractical, implausible, far-fetched, impracticable, unworkable, unbearable, intolerable, unendurable, unsustainable, unmanageable, intractable, recalcitrant, wayward, objectionable, difficult, demanding, awkward, perverse, ungovernable

Antonyms: possible, attainable, bearable, tolerable, manageable, easy to please