Definition of white lettuce in US English:

white lettuce

noun

  • 1Any of various whitish-flowered plants of the genus Prenanthes, allied to the lettuces (genus Lactuca), especially the rattlesnake-root, P. alba).

  • 2A pale-leaved cultivar of the genus Lactuca.

Origin

Mid 18th century; earliest use found in Richard Mead (1673–1754), physician and collector of books and art.