Not workable, especially not capable of being put into practice successfully; not practicable

an unworkable scheme.

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"[syn: impracticable ]

adjective

impracticable , impractical , unattainable , unrealizable , unthinkable , unnegotiable , unserviceable , unusable , useless