Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
‡ acūpĕdius, “dicebatur, cui praecipuum erat in currendo acumen pedum,” swift of foot, Paul. ex Fest. p. 9 Müll. [qs. acer + pes; cf. Gr. ὀξύπους, ὠκύπους].