From Longman Dictionary of Contemporary Englishcubitcu‧bit /ˈkjuːbɪt/ noun [countable] TMan ancient unit for measuring length, equal to the length of your arm between your wrist and your elbow
Examples from the Corpus
cubit• An 18-inch cubit gives the measurement as 450 x 76 x 45 feet or 137 x 23 x 14 metres.Origin cubit (1300-1400) Latin cubitum “elbow, cubit” 