The Collaborative International Dictionary
Reversing gear
Reversing \Re*vers"ing\, a. Serving to effect reversal, as of motion; capable of being reversed.
Reversing engine, a steam engine having a reversing gear by means of which it can be made to run in either direction at will.
Reversing gear (Mach.), gear for reversing the direction of rotation at will.
Wikipedia
Reversing gear
On a steam locomotive, the reversing gear is used to control the direction of travel of the locomotive. It also adjusts the cutoff of the steam locomotive.
Usage examples of "reversing gear".
Compass Rose hit the knuckle of the jetty - fortunately not very hard - on her way out of dock, owing to a small defect in her reversing gear.