Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
† archĭpīrāta, ae, m., = ἀρχιπειρατής, a leader of pirates, Cic. Off. 2, 11, 40; so id. Verr. 2, 5, 25; 2, 5, 29; Liv. 37, 11.