- Mother's Day is a day in May when mothers are celebrated and honored in the United States.
The second Sunday in May, when mothers are celebrated and honored in the U.S., is an example of Mother's Day.
Mother's Day definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
the second Sunday in May, a day set aside (in the U.S.) in honor of mothers
Mother's Day definition by American Heritage Dictionary
The second Sunday in May, observed in the United States as a day honoring mothers.