Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
prīmaevus, a, um, adj. [primus-aevum, in the first period of life, young, youthful (poet. and late Lat.): primaevus Helenor, Verg. A. 9, 545: natus, Cat. 64, 401: Helix, Val. Fl. 6, 570: vix primaevus eras, cum, etc., Claud. I. Cons. Stil. 1, 51: corpus, Verg. A. 10, 345; Luc. 6, 562: corpora, Val. Fl. 2, 653: flos, Verg. A. 7, 162: recepisti primaevus originis tuae florem, Amm. 15, 8, 11: adulescens, id. 16, 1, 5.