copperas

noun

cop·​per·​as ˈkä-p(ə-)rəs 

: ferrous sulfate

Word History

Etymology

Middle English coperas, from Anglo-French coperose, from Medieval Latin cuprosa, probably from aqua cuprosa, literally, copper water, from Late Latin cuprum

First Known Use

14th century, in the meaning defined above

Medical Definition

copperas

noun

cop·​per·​as ˈkäp-(ə-)rəs 

: a green hydrated ferrous sulfate FeSO₄·7H₂O used especially in making inks and pigments

—used especially of commercial grades not to be used internally