- unable, not able - (usually followed by `to') not having the necessary means or skill or know-how; "unable to get to town without a car"; "unable to obtain funds"
Antonym: able
- unable - (usually followed by `to') lacking necessary physical or mental ability; "dyslexics are unable to learn to read adequately"; "the sun was unable to melt enough snow"
Antonym: capable (indirect, via incapable)
- ineffective, ineffectual, unable - lacking in power or forcefulness; "an ineffectual ruler"; "like an unable phoenix in hot ashes"
Antonyms: potent, strong (indirect, via impotent)