por·tu·lac·a (pôr'chə-lāk'ə, pōr'-) n. Any of various fleshy plants of the genus Portulaca, especially P. grandiflora of South America, cultivated for its showy colorful flowers that open only in sunlight. Also called rose moss.
[Middle English, from Latin portulāca, purslane, from portula, diminutive of porta, gate (from the gatelike covering of the seed capsule); see per-2 in Indo-European roots.]