catback

Etymology
, sense 2 (the back of a cat, for riding upon) is modelled on.

Noun

 * 1)  The totality of components which exhaust gases flow through after exiting a vehicle's catalytic converter.
 * 2)  The back of a cat (for riding upon).
 * 1)  The back of a cat (for riding upon).
 * 1)  The back of a cat (for riding upon).