not having enough strength, influence etc (to do something or prevent, act, change etc something); (of a man) incapable of sexual intercourse

disabled; unable to perform action

not producing the effect(s) desired

useless

(of) an animal without a backbone or spinal column, e.g. insects, worms

weak, useless

(of a person, expression) looking ill, sad, tired, anxious; (of light, the sky) pale; not bright

colorless, weak

(of the body) having little power or energy; (of the mind) not confident, sure or determined; easily broken, damaged etc; easily defeated or changed

not strong