Also called romaine lettuce, cos, cos lettuce.a variety of lettuce, Lactuca sativa longifolia, having a cylindrical head of long, relatively loose leaves.
ro·maine (rō-mān') n. A cultivar of lettuce (Lactuca sativa) having a slender head of oblong or obovate leaves with broad midribs. Also called cos1, cos lettuce.
[French, from feminine of Romain, Roman, from Old French, from Latin Rōmānus, from Rōma, Rome.]
1907, from Fr. romaine (in laitue romaine, lit. "Roman lettuce"), from fem. of O.Fr. romain "Roman," from L. Romanus "Roman." Perhaps so called because of the lettuce's introduction into France (by Bureau de la Rivière, chamberlain of Charles V and VI) at the time of the Avignon papacy (1309-77).