Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
ăcĕo, ui, 2, v. n. [v. 2. acer], to be sour.
1. ăcer, ĕris, n. [kindred with Germ. Ahorn] (f. Serv. ap. Prisc. p. 698 P.),
† ăcērus, a, um, adj., = ἄκηρος, without wax: mel acerum, which flows spontaneously from the comb, Plin. 11, 15, 15, § 38 lec. dub.
2. ăcus, ĕris, n. (also, ūs, f., v. 1. acus, III.) [kindred with acus, ūs, Goth. ahana, old Norse agn, old Germ. Agana], = ἄχυρον, the husk of grain and of pulse; chaff, Cato, R. R. 54, 2; Varr. R. R. 1, 52; 57; 3, 9, 8.