Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
Glaesārĭa (Glēs-), ae (sc. insula), f. [glaesum], an amber island in the North Sea, also called Burcana, Plin. 4, 13, 27, § 97; 37, 3, 11, § 42.