Assonances refer to the repetition of vowel sounds in quick succession. Therefore, antonyms for this term would consist of words that are either unrelated or the opposite of assonance. Some antonyms that come to mind include cacophony, dissonance, and harshness. Cacophony refers to a harsh and unpleasant sound, while dissonance describes a lack of harmony or agreement. Harshness implies a rough, unpleasant quality that is unmelodious. These antonyms are useful in helping to convey a different sense or feeling from a piece of writing that employs assonance, whether it be jarring and discordant or simply lacking in harmony.