[kraws-staf, -stahf, kros-]

noun, plural cross-staffs, cross-staves. Astronomy.

an instrument for measuring the angle of elevation of heavenly bodies, consisting of a calibrated staff with another shorter staff perpendicular to and sliding on it.

Origin of cross-staff

1400–50, for an earlier sense; late Middle English
Also called forestaff, Jacob's staff. Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for cross-staff

Historical Examples of cross-staff