'Psilopsida' definitions:
Definition of 'Psilopsida'
(from WordNet)
noun
Whisk ferns; comprising the family Psilotaceae or Psilotatae: vascular plants with no roots, partial if any leaf differentiation, and rudimentary spore sacs [syn: Psilopsida, class Psilopsida, Psilotatae, class Psilotatae]