The Collaborative International Dictionary of English v.0.48:

Self-will \Self`-will"\, n. [AS. selfwill.]
   One's own will, esp. when opposed to that of others;
   obstinacy.
   [1913 Webster]

WordNet (r) 3.0 (2006):

self-will
    n 1: resolute adherence to your own ideas or desires [syn:
         stubbornness, bullheadedness, obstinacy,
         obstinance, pigheadedness, self-will]
    2: the trait of resolutely controlling your own behavior [syn:
       self-control, self-possession, possession, willpower,
       will power, self-command, self-will]