trailer car

noun Railroads.
  1. a second flatcar used for transporting an object or objects of excessive weight or length.
  2. a passenger car, not self-propelled, included in a train of self-propelled cars.

Origin of trailer car

An Americanism dating back to 1885–90
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018