wheelhorse

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.Examples: "The off wheel-horſe a grey, named Single Peeper, ſold for 50 [guineas] […] The near wheel-horſe cheſnut, named Chance."; "The driver […] neither knew any thing, said any thing, or did any thing but watch a dozen equine ears, and keep six reins taut in his hands, and coax the off wheel[-]horse with the belly of his whip-lash every two minutes, invariably accompanying the stroke with a tremendous solitary cluck."; "“Ay! he med well say that,” repeated the wagoner, still digesting the pleasure of Ben Lee’s compliment, and slapping the wheel[-]horse’s vast flank, so that the fairy chime began again, and the smack resounded like an accompaniment to its music."Synonyms: wheelerUSdated

2. (US, figuratively) A person who labors heavily for a particular cause, without being concerned about recognition.Examples: "[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.""; "A medical journal, it seems to the writer, should be a medium for the propagation of useful knowledge, the instruction of the profession in the best and most scientific methods of fighting disease; and who is so well qualified for the work as the old wheelhorses, the men who have grown gray in the fight?"; "I can't understand why an old wheel-horse like Elsworth should kick over the traces that way."USfiguratively

3. (obsolete or historical) A foot-propelled vehicle; a bicycle.Examples: "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, and whilst the roads continued dry and hard M. Dreuze could congratulate himself on the success of his invention; but with wet weather came bad roads, and to the wet succeeded frost and snow. A little extra labour was all that was required to overcome the extra friction of the bad roads, but the wheels refused to progress on the slippy frozen surface."; "As in most other accomplishments, practice alone can make a skilful rider of velocipedes. The tyro can, however, profit by the experience of others, and I give a few rules for his guidance, as well as directions for his practice. The first point is to gain confidence in, and familiarity with, his wheel horse."historicalobsolete