n. The process of adopting a more casual approach to traditionally non-casual events or situations, particularly regarding clothes.
Other Forms
While dress-down Fridays have contributed to the casualization of the American workplace, they have also led to upgrading of casual clothes.
—“Teen Boys Have Slob Appeal,” The Boston Herald, May 21, 1998
The casualization of Easter clothing is underscored by the widespread use this year of denim as a trim and as a main ingredient.
—Anne Brakster, “ A parade of clothes for kids,” Newsday (New York), April 06, 1995
1990 (earliest)
The National Restaurant Association reports that business is generally flat and that growth is in cheaper, less formal restaurants.

"The casualization of the American restaurant is the most important trend that is happening," said Jeff Prince, the senior director of the trade association in Washington."
—Marian Buros, The New York Times, January 17, 1990