Antonyms for the phrase "were jubilant" would be words that express the opposite of jubilation, such as sad, disappointed, downcast, melancholic, morose, and dejected. Instead of being filled with joy and happiness, those who feel the opposite of jubilation would be experiencing feelings of despair, depression, hopelessness, or discontent. Their emotions would range from mild disappointment to intense grief, depending on the situation. For example, losing a job, failing an exam or breaking up with a partner could lead to feeling dejected or despondent, contrasting with the feeling of being elated and overjoyed that characterizes jubilation.