WordWeb Online

1. Make calm or still
   "tranquilize the dragons of worry and fear";
   - calm, calm down, quiet, tranquillize, tranquillise [Brit], quieten [Brit], lull, still
    
2. Cause to be calm or quiet as by administering a sedative to
   "The patient must be tranquilized before the operation";
   - sedate, calm, tranquillize, tranquillise [Brit]

Derived forms: tranquilizing, tranquilized, tranquilizes

Type of: affect, comfort, console, solace, soothe

Encyclopedia: Tranquilize