1. reliable, hardworking people who do most of the work in an organization or group
Usage: informal
2. horses positioned nearest the wheels of a vehicle in a team of draft animals
Usage: historical; literal sense

Examples

• The committee’s wheelhorses stayed late to finish the project.
• She’s one of the party’s most dependable wheelhorses.
• Without these wheelhorses, the campaign would have failed.
• The organization relies on its wheelhorses to handle daily operations.
• In the old days, wheelhorses were specially trained for their position.
• The farmer hitched his strongest animals as wheelhorses.