Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
plērus, a, um, adj. [root ple-, v. plenus], very many, a very great part, most (anteclass. prim. form, for the class. plerusque, plerique): ager, campestris plerus, for the most part, Cato ap. Prisc. p. 668 P.: pater Achaeos in Caphareis saxis pleros perdidit, Pac. ib.: plera pars, id. ib. and ap. Fest. p. 230 Müll.: minores magistratus partiti iuris ploeres in ploera sunto, Cic. Leg. 3, 3, 6.
Neutr. adverb.: plerum (like plerumque, v. plerusque), for the most part, mostly, commonly: fieri solet plerum, ut, etc., Asell. ap. Prisc. p. 668 P.