Main Entry: al·i·dade

Pronunciation: \ˈa-lə-ˌdād\

Function: noun

Etymology: Middle English allidatha, from Medieval Latin alhidada, from Arabic al-ʽiḍāda 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