Meaning of Rockwell number

Rock'well num"ber

Pronunciation: [key]
— Metall. Metall.
  1. a numerical expression of the hardness of a metal as determined by a test made by indenting a test piece with a Brale, or with a steel ball of specific diameter, under two successive loads and measuring the resulting permanent indentation.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.