work ‧ horse /ˈwɜːkhɔːs $ ˈwɜːrkhɔːrs/ BrE AmE noun [countable]
a person, machine, or vehicle that does a lot of work, especially when it is hard or boring:
The Hercules aircraft has been the workhorse of the air force for over 25 years.
work ‧ horse /ˈwɜːkhɔːs $ ˈwɜːrkhɔːrs/ BrE AmE noun [countable]
a person, machine, or vehicle that does a lot of work, especially when it is hard or boring:
The Hercules aircraft has been the workhorse of the air force for over 25 years.
Longman Dictionary of Contemporary English. Longman - Словарь современного английского языка. 2012