Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
orthŏmastĭus, a, um (= ὀρθομάστιος, from ὀρθός, μαστός), high-breasted: mammarum effigie orthomastia mala, a kind of large apple, Plin. 15, 14, 15, § 51.