Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
ampullācĕus, a, um, adj. [ampulla], in the form of a flask, big-bellied: a collo ampullacea (pira) appellant, a tankardpear, Plin. 15, 15, 16, § 55; so Col. 8, 2, 15.