a.
1.
Impracticable, unfeasible, unattainable, unachievable, out of the question.
2.
Inconceivable, unthinkable, that cannot be, incapable of occurring or of being so, absurd, self-contradictory.
IMPOSSIBLE
Meaning of IMPOSSIBLE in English
Soule. Dictionary of English synonyms. Словарь английских синонимов. 2012