Dictionary.net

• A subdivision of the British Upper Silurian lying below the Old Red Sandstone; - so named from the Ludlow, in Western England. See the Chart of Geology.

2010 - New Age Dictionary Database
By Oddity Software

• A subdivision of the British Upper Silurian lying below the Old Red Sandstone; - so named from the Ludlow, in Western England. See the Chart of Geology.

1913 - Webster's Revised Unabridged Dictionary
By Noah Webster.