not possible; unable to be, exist, happen, etc.

unable to be done, performed, effected, etc.

an impossible assignment.

incapable of being true, as a rumor.

not to be done, endured, etc., with any degree of reason or propriety

an impossible situation.

utterly impracticable

an impossible plan.

hopelessly unsuitable, difficult, or objectionable.

adjective

achievable , believable , obtainable , possible , reasonable , tenable , behaving , good , governable , manageable , tolerable

adjective

absurd , beyond , contrary to reason , cureless , futile , hardly possible , hopeless , hundred-to-one , impassable , impervious , impracticable , impractical , inaccessible , inconceivable , inexecutable , infeasible , insurmountable , irrealizable , irreparable , no-go , not a prayer , no-way , no-win , out of the question , preposterous , too much , unachievable , unattainable , uncorrectable , unfeasible , unimaginable , unobtainable , unreasonable , unrecoverable , unthinkable , unworkable , useless , visionary , way out , egregious , improper , incongruous , ludicrous , objectionable , offensive , outrageous , unacceptable , unanswerable , undesirable , unsuitable , unrealizable , insufferable , insupportable , intolerable , unendurable , unsufferable , unsupportable , balky , contrarious , difficult , froward , ornery , perverse , wayward , chimerical , fantastic , insoluble , insuperable , invincible , unbearable , unrealistic , unsurpassable , untenable