any of various plants of the genus Lactuca
"The chef carefully selected crisp heads of lettuce from the garden for tonight's salad bar."
leaves of any of various plants of Lactuca sativa
"The chef tossed crisp lettuce into the salad bowl before drizzling it with dressing."
An edible plant, Lactuca sativa and its close relatives, having a head of green and/or purple leaves.
"She carefully washed the crisp lettuce before adding it to her summer salad."