silencer
n
(a) (Brit) (US muffler) device that reduces the noise made by a vehicle's exhaust （机动车的）消声器. =>illus at App 1 见附录1插图, page xii.
(b) device that reduces the noise made by a gun being fired （枪的）消声器. silence interj be quiet 安静; 别出声
`Silence!' shouted the teacher. ｀安静!＇教师喊道.