What is the meaning of Silencer?

Something that silences or (notionally) nearly silences.

2. An attachment to a gun that reduces the sound it emits.

   An attachment to a gun that reduces the sound it emits.

   The muffler of an internal combustion engine.

   Any of various devices to silence the humming noise of telegraph wires.

   Something that prevents or greatly reduces gene expression.

   Source: wiktionary.org