Antonyms are words that have opposite meanings to a particular word. In the case of "was jubilant," some antonyms would be "was dejected," "was glum," "was despondent," and "was melancholy." Instead of feeling joyful, elated, or exultant, a person who was dejected or glum would feel downcast, sad, or unhappy. Likewise, someone who was despondent or melancholy would feel hopeless, dispirited, or gloomy. Opposite meanings of a word help to convey a different tone, mood, or attitude towards a situation. Therefore, depending on the context, the antonyms for "was jubilant" could be used to express a range of emotions and reactions.