Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
† cāpo, ōnis (access. form cāpus, i, Varr. R. R. 2, 7, 15; 3, 9, 3; Col. 8, 2, 3), m., = κύπων, a capon, Varr. l. l.; Col. l. l.; Mart. 3, 58, 38; Pall. Nov. 1, 3; Apic. 4, 3.
cāpus, i, v. capo.