a) Not efficient; not producing the effect intended or desired; inefficacious; as, inefficient means or measures.
Celery is an inefficient food.
b) Incapable of, or indisposed to, effective action; habitually slack or remiss; effecting little or nothing; as, inefficient workers; an inefficient administrator.
Jessica was terribly inefficient at cleaning, so her brother usually had to clean the whole room.
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