serf

noun3

1. •
   A partially free peasant of a low hereditary class, attached like a slave to the land owned by a feudal lord and required to perform labour, enjoying minimal legal or customary rights.

   • See how the serfs work the ground / And they give it all they’ve got — 2012
2. •
   A similar agricultural labourer in 18th and 19th century Europe.
3. •
   A worker unit.