WordWeb Online

1. Noisy and lacking in restraint or discipline
   "a boisterous crowd"
   - rambunctious [N. Amer], robustious, rumbustious [Brit], unruly
    
2. Full of rough and exuberant animal spirits
   "boisterous practical jokes"
   - knockabout
    
3. Violently agitated and turbulent
   "boisterous winds and waves"
   - fierce, rough

See also: boisterously, boisterousness, disorderly, spirited, stormy