impossible -
something that cannot be done; "his assignment verged on the impossible"
Adjective
impossible -
not capable of occurring or being accomplished or dealt with; "an impossible dream"; "an impossible situation"
possible capable of happening or existing; "a breakthrough may be possible next year"; "anything is possible"; "warned of possible consequences"
hopeless (informal to emphasize how bad it is) beyond hope of management or reform; "she handed me a hopeless jumble of papers"; "he is a hopeless romantic"
impractical not practical; not workable or not given to practical matters; "refloating the ship proved impractical because of the expense"; "he is intelligent but too impractical for commercial work"; "an impractical solution"
hopeless (informal to emphasize how bad it is) beyond hope of management or reform; "she handed me a hopeless jumble of papers"; "he is a hopeless romantic"
impracticable,
infeasible,
unfeasible,
unworkable not capable of being carried out or put into practice; "refloating the sunken ship proved impracticable because of its fragility"; "a suggested reform that was unfeasible in the prevailing circumstances"