n. In botany, a form of inflorescence in plants, in which the flowers are closely arranged in a spike or head which has a fleshy or thickened rachis.n. In zoology:n. The hectocotylus of the male cephalopod: a specialized part of the fore foot, on one side, which becomes hectocotylized, or assumes a sexual function. On the opposite side is a corresponding part, not subject to hectocotylization, called the antispadix.n. In Hydrozoa, the manubrium of the hydromedusans, an offset of a blastostyle bearing the genital products, like the part of a pea-pod which bears the peas.n. A genus of cœlenterates.