Spontaneity is a quality that describes anything that happens without pre-planning or forethought. Synonyms for this word can include words like impulsiveness, unpredictability, and impetuosity. These words all describe the same quality of making decisions or taking action without much thought or planning ahead of time. Other synonyms for spontaneity might include words like unrestrained, uninhibited, or suddenness. These words all suggest a sense of freedom or excitement that comes from making decisions or taking actions without worrying about the consequences. No matter what word you choose to describe spontaneity, it is clear that this quality can add energy and excitement to any situation.