| Noun | 1. | genus Lactuca - an herb with milky juice: lettuce; prickly lettuceasterid dicot genus - genus of more or less advanced dicotyledonous herbs and some trees and shrubs aster family, Asteraceae, Compositae, family Asteraceae, family Compositae - plants with heads composed of many florets: aster; daisy; dandelion; goldenrod; marigold; lettuces; ragweed; sunflower; thistle; zinnia lettuce - any of various plants of the genus Lactuca common lettuce, garden lettuce, Lactuca sativa - annual or perennial garden plant having succulent leaves used in salads; widely grown cos lettuce, Lactuca sativa longifolia, romaine lettuce - lettuce with long dark-green spoon-shaped leaves head lettuce, Lactuca sativa capitata - distinguished by leaves arranged in a dense rosette that develop into a compact ball |