The term 'be decked' refers to the act of dressing or decorating oneself or a place with ornaments, jewels, or other embellishments. The antonyms of be decked are undecorated, plain, unadorned, and unembellished. These antonyms describe a lack of embellishment, and often convey simplicity, minimalism, or even dullness. For instance, an undecorated room may be devoid of any paintings, tapestries, or art pieces, while a plain dress may not have any intricate patterns or embroideries. While the word 'be decked' suggests an elaborate and ornate appearance, the antonyms describe a more straightforward and straightforward approach.