Pronunciation: (krôs'staf", -stäf", kros'-), [key]
—pl. -staffs, -staves. Astron.
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. Also called forestaff, Jacob's staff.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.