Meaning of cross-staff

cross-staff

Pronunciation: (krôs'staf", -stäf", kros'-), [key]
— pl. -staffs, -staves.
  1. 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
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.