Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
† aspis, ĭdis, f. (acc. Gr. aspida, Luc. 9, 701; plur. aspidas, Cic. N. D. 3, 19, 47) [ἀσπίς, com. shield, rarely an asp; this order of frequency is reversed in Lat.].