Definition of "underbody"

“There was somebody’s entire fender or underbody on the racetrack,” he said.

2007 May 14, Viv Bernstein, “Engine Woes Fail to Slow Hendrick Team’s Streak”, in New York Times‎

The rest were undergoing special underbody cleaning safety checks at TfW depots, after speculation that the cause of the incidents may have been a build-up of engine oil and combustible material such as fallen leaves and general detritus.

2023 March 22, “Network News: Class 175s withdrawn for safety checks after fires”, in RAIL, number 979, page 13