Definition of sea lettuce:
(n) :
Any of several edible seaweeds of the genus Ulva.
(n) :
Similar seaweed species of other genera:
(n) :
Monostroma spp., also known as the slender sea lettuce, a kind of algae.
(n) :
Scaevola taccada, also known as the beach cabbage, a terrestrial flowering plant species that is native to coastal regions of the Indo-Pacific.
(n) :
Dudleya caespitosa, also known as the sand lettuce, a terrestrial flowering plant species that is endemic to coastal areas of California