• (n.) An instrument formerly used at sea for taking the altitudes of heavenly bodies, now superseded by the sextant; -- called also cross-staff. Found on http://thinkexist.com/dictionary/meaning/forestaff/
Fore'staff` noun (Nautical) An instrument formerly used at sea for taking the altitudes of heavenly bodies, now superseded by the sextant; -- called also cross-staff . Brande & C. Found on http://www.encyclo.co.uk/webster/F/61