A distilled (see distillation) liquor made primarily from barley (malted or unmalted) as well as corn, rye, wheat and oats. Irish whiskeys are triple-distilled for extra smoothness and are in casks for a minimum of 4 (usually 7 to 8) years. The aging casks have typically been used previously for aging bourbon, sherry or rum, the flavors of which contribute unique nuances to the whiskey.
From The Food Lover's Companion, Fourth edition by Sharon Tyler Herbst and Ron Herbst. Copyright © 2007, 2001, 1995, 1990 by Barron's Educational Series, Inc.