Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
† mĕsŏchŏrus, i, m., = μεσόχορος, one who stands in the middle of a chorus (of dancers or singers) to lead it, a chorusleader (post-class.): cum mesochorus dedit signum, Plin. Ep. 2, 14, 7; Sid. Ep. 1, 2; Schol. Juv. 11, 172.