From nl. theodolitus (1571), perhaps containing Ancient Greek θέᾱ and Arabic عِضَادَة; if so, doublet of alidade.

• IPA: /θiːˈɒdəlaɪt/

theodolite (plural theodolites)

1. A surveying instrument, consisting of a small mounted telescope, used to measure horizontal and vertical angles.
   • 1839, Robert FitzRoy, Phillip Parker King, Narrative of the Surveying Voyages of His Majesty’s Ships Adventure and Beagle, between the Years 1826 and 1836, […], volume II, London: Henry Colburn, […], →OCLC ↗, page 356 ↗:

     The height of those mountains was from five to seven thousand feet above our level, by angular measurement with a theodolite.

   • 1895–1897, H[erbert] G[eorge] Wells, “What I Saw of the Destruction of Weybridge and Shepperton”, in The War of the Worlds, London: William Heinemann, published 1898, →OCLC ↗, book I (The Coming of the Martians), page 91 ↗:

     It was a lieutenant and a couple of privates of the 8th Hussars, with a stand like a theodolite, which the artilleryman told me was a heliograph.

• French: théodolite
• German: Theodolit
• Italian: teodolite
• Portuguese: teodolito
• Russian: теодоли́т
• Spanish: teodolito