Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
cōpa (cūpa), ae, f. [copo = caupo], a female tavern-keeper and castanet-dancer, who exhibited her arts in her ale-house (cf. crotalum), Verg. Cop. 1 Heyne and Wagner: matronae copas imitantes, Suet. Ner. 27.