The Chicago Assyrian Dictionary, a publication of the Oriental Institute at the University of Chicago, is a comprehensive dictionary of the various dialects of Akkadian, one of the earliest known Semitic language recorded on cuneiform texts that date from c. 2400 B.C. to A.D. 100. These texts, which were recovered from archaeological excavations of ancient Near Eastern sites, cover areas from law to magical incantations and medicinal formulas.
The dictionary, also known mainly as the CAD in academia, is more than just a word-for-word translation guide. Each entry covers all aspects of the word in question, from the time period where the word was used to which forms of the verb are attested in what literary genres.
The dictionary is a work in progress to this day, initiated in 1921 by James Henry Breasted, and there are still four of the projected 21 volumes to be completed. The dictionary will end up at over 7,000 pages for a project that was in the '20s expected to be under half that length.