1. rat run - Noun
2. rat run - Verb
rat run (plural rat runs)
(idiomatic) A small, usually minor road used by a significant amount of traffic as a short cut or to avoid congestion on more major routes.
rat run (third-person singular simple present rat runs, present participle rat running, simple past rat ran, past participle rat run)
(idiomatic) To drive through residential streets to avoid congestion on the main roads.