The Collaborative International Dictionary
Forestaff
Forestaff \Fore"staff`\, n. (Naut.)
An instrument formerly used at sea for taking the altitudes
of heavenly bodies, now superseded by the sextant; -- called
also cross-staff.
--Brande & C.
Wiktionary
forestaff
n. (context nautical English) An instrument formerly used at sea for taking the altitudes of heavenly body, later replaced by the sextant.