a North American songbird of the American blackbird family, with a bill resembling that of a finch. The bobolink is a small New World blackbird and the only member of the genus Dolichonyx. Bobolink definition is - an American migratory songbird (Dolichonyx oryzivorus) with the breeding male chiefly black. The bobolink (Dolichonyx oryzivorus) is a small New World blackbird and the only member of the genus Dolichonyx.