Decorate, dress up, as in They were all decked out in their best clothes. [Mid-1700s]
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
How to use deck out in a sentence
They must not be compelled to deck out their houses in honor of religious processions, nor to swear on St. Anthony's arm.History of the Rise of the Huguenots | Henry Baird
For an instant she had the naïve, melodramatic instinct of youth to deck out its little events in the guise of crises.The Squirrel-Cage | Dorothy Canfield
The French chamarrer, to deck out, or bedizen, is said to be a word of kindred origin.The Bible in Spain - Vol. 2 [of 2] | George Borrow
But she used to shut herself up in her room in the evenings and deck out for Mr. Sam in her best things.Where There's A Will | Mary Roberts Rinehart
Inga, Mildrid's cousin, herself a married woman now, had come to deck out the bride.The Bridal March; One Day | Bjrnstjerne Bjrnson