What is "stench trap"

Stench \Stench\, n. [AS. stenc a strong smell, fr. stincan. See Stink, v. i.]

1. A smell; an odor. [Obs.]

   Clouds of savory stench involve the sky.
   --Dryden.

2. An ill smell; an offensive odor; a stink.
   --Cowper.

   Stench trap, a contrivance to prevent stench or foul air from rising from the openings of sewers, drains, etc.

n. A device to prevent foul air from rising from the openings of sewers, drains, etc.