WordWeb Online

1. Done by design
   "wilful disobedience";
   - willful [N. Amer]
    
2. Habitually disposed to disobedience and opposition
   "The relationship between the intellect and the emotions is like the relationship between parents and their wilful five-year-old";
   - froward [archaic], headstrong, self-willed, willful [N. Amer]

See also: disobedient, voluntary