Fullblown means fully developed or fully matured. Antonyms for the word fullblown are incomplete, undeveloped, immature, or fledgling. Incomplete refers to something that is partially done or lacks some essential elements. Undeveloped implies unfinished or not fully grown, while immature suggests a lack of maturity or sophistication. Fledgling means a novice or beginner who is still learning and not yet fully capable. These words are opposite to fullblown and may be used in different contexts depending on the situation. When using antonyms for fullblown, you should choose the most appropriate word that best fits the context.