Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
bestĭārĭus, a, um, adj. [id. I. B.], of or pertaining to beasts: ludus, a fight with beasts, Sen. Ep. 70, 20; 70, 22.
Usu. as subst.: bestĭārĭus, ii, m., one who fights with wild beasts in the public spectacles, a beast-fighter, θηριομάχης (persons hired, or criminals: the former with weapons, and as victors rewarded; the latter, unarmed, and sometimes bound, Vop. Aur. 37; Tert. Pud. 22): praeclara aedilitas! Unus leo, ducenti bestiarii, Cic. Sest. 64, 135: gladiatoribus et bestiariis obsedere rem publicam, id. Vatin. 17, 40; so id. Q. Fr. 2, 6, 5; Sen. Ben. 2, 19, 1: ludus bestiariorum, Sen. Ep. 70, 17; * Suet. Claud. 34.