The term "jazzes up" refers to adding excitement or interest to something. Its antonyms would be words that describe making something dull or uninteresting. Such antonyms include "dulls," "boring," "tires," "fatigues," or "saddens." These words are associated with a lack of energy, creativity or enthusiasm, since their main function is to dampen the excitement or liveliness of something. These antonyms can be used in a sentence to explain how a new policy or idea may be received by employees or colleagues. While some may be excited by it, others may find it dull or uninteresting, and this opposition adds depth and perspective to the situation.