wheel-horse

Noun

wheelhorse (plural wheelhorses)

1. (US, dated) One of a team of horses which is nearest to the wheels of a carriage, as opposed to a leader or forward horse.
   • The off wheel-horſe a grey, named Single Peeper, ſold for 50 [guineas] […] The near wheel-horſe cheſnut, named Chance.1750 October, “A Description, with the Form, of the Four Wheel Carriage, which was Drawn at Newmarket, 19 Miles in 54 Minutes. […] Invented by Mr J. Wright in Long Acre.”, in Sylvanus Urban...

   Synonyms:

   wheeler

2. (US, figuratively) A person who labors heavily for a particular cause, without being concerned about recognition.
   • [F]rom his [Benjamin Ruggles'] well-known habits of industry and constant devotion to the interests of his constituents, he was called "The Wheelhorse of the Senate."1866, Charles Lanman, “Ruggles, Benjamin”, in Dictionary of the United States Congress, Compiled as a Manual of Reference for the Legislator and Statesman, 3rd rev. edition, [Washington, D.C.]...
3. (historical, obsolete) A foot-propelled vehicle; a bicycle.
   • In 1830 a bold and vigorous attempt was made to utilize the wheel-horse. A French post-office official, M. Dreuze by name, brought forward an improvement on the old two-wheel velocipede, which bid fair to be successful. […] A number of the country letter-carriers were mounted on the wheel-horse...1869, Velox [pseudonym], “The Velocipede of the Past”, in Velocipedes, Bicycles, and Tricycles: How to Make and How to Use Them. With a Sketch of their History, Invention, and Progress, London...