n.
Pronunciation: ' a-l ə - ˌ d ā d
Function: noun
Etymology: Middle English allidatha, from Medieval Latin alhidada, from Arabic al-'i ḍ ā da the revolving radius of a circle
Date: 15th century
: a rule equipped with simple or telescopic sights and used for determination of direction: as a : a part of an astrolabe b : a part of a surveying instrument consisting of the telescope and its attachments