What does duodēvīgintī mean in Latin?

duodēvīgintī, a numeral, means “eighteen; 18”.

How do you pronounce duodēvīgintī?

In classical Latin, [du.ɔ.deː.wiːˈɡɪn.tiː]; in ecclesiastical (church) Latin, [du.o.de.viˈd͡ʒin.ti].

numeral

duodēvīgintī (indeclinable)

Classical[du.ɔ.deː.wiːˈɡɪn.tiː]Ecclesiastical[du.o.de.viˈd͡ʒin.ti]

Mille Verba core vocabulary

indeclinableeighteen; 18
castra in altitudinem pedum XII vallo fossaque duodeviginti pedum muniri iubet.He orders him to fortify a camp with a rampart twelve feet in height, and a trench eighteen feet in breadth.c. 52 BCE, Julius Caesar, Commentarii de bello Gallico 2.5
G. et L. in duodeviginti mensium spatio amisit ambos, Gaio in Lycia, Lucio Massiliae defunctis.He lost Gaius and Lucius within the span of eighteen months, for the former died in Lycia and the latter at Massilia.121 CE, Suetonius, De vita Caesarum divi Augusti 65

dŭŏ-dē-vīginti,

I. card. num., eighteen, Plaut. Poen. 4, 2, 74 sq.; Cic. Ac. 2, 41, 128; id. Rep. 2, 22; Caes. B. G. 2, 5 fin.; id. B. C. 3, 71 al.; cf. also: annis mille centum et duobus de viginti fere, etc., Eutr. 10, 9.

Literally "two from twenty"; from duo (“two”) + dē (“from”) vīgintī (“twenty”). Compare non-subtractive form octōdecim.