Impracticable

impossible unworkable unfeasible idealistic theoretical visionary romantic wild absurd inapplicable inoperable useless unattainable improbable infeasible nonviable quixotic speculative unreal abstract illogical chimerical otherworldly starry-eyed inappropriate inefficacious unserviceable unbusinesslike unusable unwise irrealizable no-go nonfunctional out of the question won’t fly ivory-tower