A silencer is when a person bunches up a bit of toilet paper, and quickly places it in the water retaining part of the toilet bowl.
Thus, was a foreign object (fecial matter) drops into the toilet, there is no splash, and therefore no noise is created, allowing the person to walk confidently out without being given terrible terrible looks.
One downside to this is that it does not protect the person from their own gaseous discharge before the act of defecation.
Guy 2 - "Hey buster, dont worry, use a silencer, its fine man, honestly, in Silencer we trust"
Guy 1 - "Than........ (fart)...... i gotta g-....... whoa nelly!"
2) An assasin that specializes in finding and eliminating a "Rat". Basically, a hitman.