undercarriage

Noun

undercarriage (plural undercarriages)

1. The supporting structural framework of a land vehicle (such as a car, truck, van, wagon, etc).
   • Near-synonym: chassis
   • The solution to coach riding defects, at least, seems to require much more co-operative practical experiment by all engineering departments to achieve better sympathy between the vehicle body, its undercarriage and the track on which it rides.1960 December, “The riding of B.R. coaches”, in Trains Illustrated, page 706

   Synonyms:

   chassis

2. The landing gear of an aircraft.
3. (euphemistic, humorous) The genitalia.
   • She had no problem imagining Nick with the zipper of his coveralls pulled low, showing his muscled chest, washboard abs, and treasure trail leading down to… well, let's just say she wouldn't mind checking out his undercarriage.2008, Robin Kaye, Romeo, Romeo, Sourcebooks, →ISBN, page 13