unable in WordNet English dictionary

1. lacking in power or forcefulness
   "an ineffectual ruler"; "like an unable phoenix in hot ashes"
   ineffective  ineffectual  unable 
   
2. (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"
   unable 
   
3. (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"
   unable