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 Oölite. See the Chart of Geology. [1913 Webster]
, n.
1 (Lias) Geol. the lower strata of the Jurassic system of rocks, consisting of shales and limestones rich in fossils.
2 a blue limestone rock found in SW England.