Plunge is a word that is often associated with sudden and significant action. It can be used to describe a sudden and steep fall, a sudden drop in temperature, or a sudden and bold action taken in a particular situation. Some of the synonyms of the word 'plunge' that may be used to add more variety and nuance to your writing include words like 'dive', 'drop', 'plummet', 'submerge', 'descend', 'immerse', 'swoop', 'fall', 'pitch', 'plunk', and 'catapult'. Each of these synonyms has its own unique connotations and usage patterns, so it is essential to choose the right word based on the context and intended meaning of your writing.