1Either of two ferns with delicate fronds, the maidenhair fern, Adiantum capillus-veneris, and maidenhair spleenwort, Asplenium trichomanes (now regional). Formerly also occasionally: †a water dropwort, genus Oenanthe (obsolete).

2Any small aquatic flowering plant of the genus Elatine (family Elatinaceae), typically found in or at the edge of shallow water, and sometimes grown in aquaria.