1. Incapable, incompetent, inefficient, unable are applied to a person or thing that is lacking in ability, preparation, or power for whatever is to be done. Incapable usually means inherently lacking in ability or power: incapable of appreciating music; a bridge incapable of carrying heavy loads. Incompetent, generally used only of persons, means unfit or unqualified for a particular task: incompetent as an administrator. Inefficient means wasteful in the use of effort or power: an inefficient manager; inefficient methods. Unable usually refers to a temporary condition of inability to do some specific thing: unable to relax, to go to a concert.

Did you mean incapable?