Originally: garden purslane, Portulaca oleracea (family Portulacaceae). Later more widely: any plant of the genus Portulaca, which comprises trailing succulent plants of warm and tropical regions, with a calyx of two sepals and brightly coloured flowers opening only in direct sunshine; especially one grown for ornament, such as the sun plant, P. grandiflora. Also (in form Portulaca): the genus itself.