WordWeb Online

1. Not producing an intended effect
   "an ineffective teacher"; "ineffective legislation";
   - uneffective, ineffectual
    
2. Lacking in power or forcefulness
   "an ineffective ruler";
   - ineffectual, unable, wet [Brit, informal], pathetic, effete, useless [informal]
    
3. Lacking the ability or skill to perform effectively; inadequate
   "an ineffective administration";
   - inefficient

See also: effectiveness, effectivity, effectuality, effectualness, idle, impotent, incompetent, inefficacious, inefficient, powerless, toothless, unproductive, useless

Antonym: effective