Lewis & Short

Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.

optĭmas (optŭm-), ātis, adj. [optimus], of or belonging to the best or noblest, aristocratic: res publica, quae ex tribus generibus illis, regali et optumati et populari confusa modice, Cic. Rep. 2, 23, 41 (from Non. 342, 31): matronae opulentae, optimates, Enn. ap. Cic. Fam. 7, 6, 1 (Trag. v 294 Vahl.).
Hence, subst.: optĭmas (optŭm-), ātis, usually in plur.: optĭmātes (optŭm-), um and ĭum, comm., the adherents of the best men, in a political sense, i. e. the aristocratic party, the aristocrats (opp. populares, the popular party; cf.: primores, proceres): qui ita se gerebant, ut sua consilia optimo cuique probarent, optimates habebantursunt principes consilii publici, sunt, qui eorum sectam sequuntur, Cic. Sest. 45, 96: cum (summa rerum) est penes delectos, tum illa civitas optimatium arbitrio regi dicitur (opp. to the regnum and the civitas popularis), id. Rep. 1, 26, 42; so, in optimatium dominatu, id. ib. 1, 27, 43: contra voluntatem omnium optimatum, id. Inv. 2, 17, 52: plebis, et optimatium certamina, Tac. A. 4, 32: omnes optimates Juda et Jerusalem, Vulg. Jer 27, 20 et saep.
In sing.: dum pudet te parum optimatem esse, Cael. ap Cic. Att. 10, 9, A, 2.