The Collaborative International Dictionary
Water lettuce
Water lettuce \Wa"ter let"tuce\ (Bot.)
A plant ( Pistia stratiotes) which floats on tropical
waters, and forms a rosette of spongy, wedge-shaped leaves.
--J. Smith (Dict. Econ. Plants).
WordNet
water lettuce
n. pantropical floating plant forming a rosette of wedge-shaped leaves; a widespread weed in rivers and lakes [syn: pistia, water cabbage, Pistia stratiotes, Pistia stratoites]