not efficient; unable to effect or achieve the desired result with reasonable economy of means.

lacking in ability, incompetent.

adjective

able , capable , competent , efficient , expert , useful

adjective

can’t hack it , careless , disorganized , extravagant , faulty , feeble , half-baked * , improficient , improvident , incapable , incompetent , ineffective , ineffectual , inefficacious , inept , inexpert , not cut out for , prodigal , shooting blanks , slack , slipshod , sloppy , slovenly , unfit , unprepared , unqualified , unskilled , unskillful , untrained , weak , inapt , unworkmanlike , useless , clumsy , fumbling , remiss , unfitted , unproductive , wasteful