unworkable
[adjective]
Synonyms: impossible, impracticable, impractical, infeasible, irrealizable, unattainable, unfeasible, unrealizable, nonfunctional, unfunctional, unserviceable, unusable, useless

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Antonyms: workable

[TahlilGaran] English Synonym Dictionary ▲

un‧work‧a‧ble /ʌnˈwɜːkəbəl $ -ɜːr-/ adjective
[Word Family: noun: work, workaholic, worker, working, WORKINGS; adjective: workable ≠ unworkable, overworked, working; verb: work, rework]
an unworkable plan, system, law etc is not likely to be successful

[TahlilGaran] Dictionary of Contemporary English ▲