inefficient
adjective
°Not efficient; not producing the effect intended or desired; inefficacious; as, inefficient means or measures.
"Celery is an inefficient food."
°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."