Lias
Lias (lī"as) , noun
[Compare French lias, from liais sort of limestone, Old French also liois; perh. of Celtic origin, compare Armor. liach, leach, a stone, Gael. leac, Welsh llech. Compare Cromlech.]
(Geology) The lowest of the three divisions of the Jurassic period; a name given in England and Europe to a series of marine limestones underlying the Oolite. See the Chart of Geology.