The Collaborative International Dictionary of English v.0.48:
Lactuca \Lac*tu"ca\, n. [L., lettuce. See Lettuce.] (Bot.) A genus of composite herbs, several of which are cultivated for salad; lettuce. [1913 Webster]WordNet (r) 3.0 (2006):
Lactuca n 1: an herb with milky juice: lettuce; prickly lettuce [syn: Lactuca, genus Lactuca]