A historical navigation instrument used by sailors to measure the altitude of the sun or stars by observing them backwards over the shoulder, eliminating the need to look directly at the sun.
Back + staff; 'staff' from Old English 'stæf' meaning stick. Invented in the 17th century as an improvement to the cross-staff instrument.
The backstaff was genius engineering—sailors could measure the sun's position without blinding themselves, which the old cross-staff method risked! It stayed in use until the sextant was invented in the 1700s.
Complete word intelligence in one call. Free tier — 50 lookups/day.