Wordnet 3.0
ADJECTIVE (1)
1. 
 tending to soothe or tranquilize; 
- Example: "valium has a tranquilizing effect"- Example: "took a hot drink with sedative properties before going to bed"[syn: ataractic, ataraxic, sedative, tranquilizing, tranquillizing, tranquilising, tranquillising]
WordNet (r) 3.0 (2006):
tranquilising
    adj 1: tending to soothe or tranquilize; "valium has a
           tranquilizing effect"; "took a hot drink with sedative
           properties before going to bed" [syn: ataractic,
           ataraxic, sedative, tranquilizing,
           tranquillizing, tranquilising, tranquillising]