Illyricum = "the lyric band"
1) a region lying between Italy, Germany, Macedonia and Thrice, having on one side the Adriatic Sea, and on the other the Danube
Part of Speech: noun proper locative
Neuter of an adjective from a name of uncertain derivation; (the) Illyrican (shore), that is, (as a name itself) Illyricum, a region of Europe: - Illyricum.
These two sites give similar information, with the definition from several dictionaries and statistics on the use of the word.
Perseus Digital Library
University of Chicago's Logion lexicon
Thayer's dictionary plus other information.
From this site's dictionary (in Italian)
Click on the first column to search for that word as a form of the root Ἰλλυρικόν; click on the second column to search for that grammatical form of the root Ἰλλυρικόν; click on the third column to search for that word and grammatical form; click on the total to search for the root Ἰλλυρικόν.