'Lias' definitions:

Definition of 'Lias'

From: GCIDE

Lias \Li"as\ (l[imac]"as), n. [Cf. F. lias, fr. liais sort of limestone, OF. also liois; perh. of Celtic origin, cf. Armor. liach, leach, a stone, Gael. leac, W. llech. Cf. Cromlech.] (Geol.) 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 O["o]lite. See the Chart of Geology. [1913 Webster]