WordNet (r) 3.0 (2006):

class Lycopsida
    n 1: club mosses and related forms: includes Lycopodiales;
         Isoetales; Selaginellales; and extinct Lepidodendrales;
         sometimes considered a subdivision of Tracheophyta [syn:
         Lycopsida, class Lycopsida, Lycopodiate, class
         Lycopodiate]