Of or pertaining to Illyria or Illyrians. / In the Illyrian language.

An extinct Indo-European language or group of languages spoken in modern Southeast Europe, in the western half of the Balkan Peninsula. / (historical or obsolete) The Serbo-Croatian language.

An inhabitant of ancient Illyria. / An inhabitant of Roman province of Illyricum (Illyro-Roman). / (obsolete) A South Slav, especially a Croat, used in 17th-19th centuries. / (uncommon) A Proto-Albanian.

plural of Illyrian

(Indo-European studies) a proposed branch within the Indo-European language family, of which the Thraco-Dacian and Illyrian branches are sub-branches.