"workhorses" in the noun sense
1. workhorse
machine that performs dependably under heavy use
"the IBM main frame computers have been the workhorse of the business world"
2. workhorse
a horse used for plowing and hauling and other heavy labor
Source: WordNet® (An amazing lexical database of English)
Princeton University "About WordNet®."
WordNet®. Princeton University. 2010.
View WordNet® License