Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
Ilergavonenses (Illurg-), ium, m., Liv. 22, 21, 6; Caes. B. C. 1, 60, 2.
Called also Ilergāŏnes, um, m., a people of Hispania Tarraconensis, on the sea-coast, near the mouth of the Ebro, Plin. 3, 3, 4, § 20.
Hence, Illurgavonensis, e, adj., of the Illurgavonenses: cohors, Caes. B. C. 1, 60, 4.