Sedative \Sed"a*tive\, a. [Cf. F. s['e]datif.] Tending to calm, moderate, or tranquilize; specifically (Med.), allaying irritability and irritation; assuaging pain.
Source: Webster's Revised Unabridged Dictionary (1913)
Sedative \Sed"a*tive\, n. (Med.) A remedy which allays irritability and irritation, and irritative activity or pain.