WordWeb Online

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

Derived forms: tranquillises, tranquillising, tranquillised

See also: tranquilliser [Brit]

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