from The American Heritage® Dictionary of the English Language, 4th Edition
- n. An indicator or a sighting apparatus on a plane table, used in angular measurement.
- n. A topographic surveying and mapping instrument used for determining directions, consisting of a telescope and attached parts.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A sighting device used for measuring angles.
from the GNU version of the Collaborative International Dictionary of English
- n. The portion of a graduated instrument, as a quadrant or astrolabe, carrying the sights or telescope, and showing the degrees cut off on the arc of the instrument.
from The Century Dictionary and Cyclopedia
- n. A movable arm passing over a graduated circle, and carrying a vernier or an index: an attachment of many instruments for measuring angles. See cut under sextant.
- n. A straight-edge carrying a telescope: an attachment of the plane-table for transferring to paper the direction of any object from the station occupied.
- n. Also written alhidade.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. surveying instrument consisting of the upper movable part of a theodolite including the telescope and its attachments
- n. surveying instrument used with a plane table for drawing lines of sight on a distant object and for measuring angles
French, from Medieval Latin alidada, sighting rod, from Arabic al-'iḍāda, the revolving radius of a circle : al-, the + 'iḍāda, revolving radius (alternate form of 'aḍud, humerus, from 'aḍada, to lop, cut (trees); see ʿṢ́d in Semitic roots).(American Heritage® Dictionary of the English Language, Fourth Edition)
From French alidade, from Spanish alidada, from Arabic عِضَادة, perhaps from عضد "upper arm". (Wiktionary)