Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
Ilergētes, um, m., a people of Hispania Tarraconensis, on the north of the Iberus, Plin. 3, 3, 4, § 21; Liv. 21, 23; 61; 22, 21; 26, 49 al.