Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
† archĭmīmus, i, m., = ἀρχίμιμος, chief mimic actor or pantomime, * Suet. Vesp. 19; so Inscr. Orell. 2625.
Hence, fem. ARCHIMIMA, ae, chief mimic actress, Inscr. Orell. 4760.