The word "subitaneous" means sudden or unexpected. Synonyms for "subitaneous" include abrupt, immediate, instantaneous, unexpected, and swift. Other synonyms for this word can be unforeseen, impulsive, impetuous, and impromptu. When applied in different contexts, its synonyms can convey the intensity of the situation, whether it be an abrupt crisis or an impulsive decision, for example. When used in writing or conversations, any of these synonyms can make the language more sophisticated and effectively convey the intended meaning. By using these synonyms, writers can add flair to their work and voice their opinions more effectively.