A Eurasian wild lettuce, Lactuca serriola (family Asteraceae), naturalized in the United States, with leaves which are deeply lobed when mature and have a distinctive row of spines on the midvein of the lower surface.
Origin
Late 18th century.
Definition of prickly lettuce in US English:
prickly lettuce
noun
A Eurasian wild lettuce, Lactuca serriola (family Asteraceae), naturalized in the United States, with leaves which are deeply lobed when mature and have a distinctive row of spines on the midvein of the lower surface.