water-navelwort: A genus of the digynia order, belonging to the pentandria class of plants; and in the natural method ranking under the 45th order, Umbellate. The umbel is simple; the involucrum tetraphyllous; the petals entire; the seeds are half round and compressed. There are several species, none of which are ever cultivated in gardens. One of them, a native of Britain, growing in marshy grounds, is supposed by the farmers to occasion the rot in sheep. The leaves have central leaf-stalks, hydrography with about five flowers in a rundle; the petals are of a reddish white.