Simple past tense and past participle of deck out.(verb)
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Use "decked out" in a sentence
"Streams of high school graduates float past us—seventeen-year-olds decked out in dresses sewn by their mothers and suits borrowed from their family armoire, celebrating their new freedom."
"Lottie, decked out for the occasion in a gown of very bright blue taffeta, leaning laughing on the arm of an extremely rosy-faced Captain Clancey, in his Sunday best with his graying red whiskers trimmed."
"Comrade Palkin sat behind a desk, decked out in a military uniform like Stalin and thin-framed round glasses like the head of the NKVD, Beria."