1) Measuring device 2) Measuring instrument 3) Measuring system 4) Used in navigation 
• (n.) An instrument for taking azimuths and altitudes simultaneously.
Alt·az'i·muth noun [ All tude + azimuth .] (Astron.) An instrument for taking azimuths and altitudes simultaneously. 
A mounting for a telescope or camera that has two, mutually perpendicular axes of rotation - one horizontal, the other vertical. This permits the telescope or camera to be slewed vertically and horizontally. A camera tripod is an example of an altazimuth mount
An altazimuth or universal transit instrument, is an astronomical instrument similar to a theodolite, having a telescope so mounted on a graduated vertical circle that it can be turned round in a plane perpendicular to the horizon, while it is also mounted so that is can also be turned horizontally to any point of the compass above a graduated hori...
[n] - an instrument that measures the altitude and azimuth of celestial bodies
noun an instrument that measures the altitude and azimuth of celestial bodies; used in navigation
an instrument for determining both the altitude and the azimuth of a heavenly body.