Pounce upon is a phrasal verb that means to attack or seize suddenly. There are several synonyms for this word including ambush, assault, attack, jump, leap, raid, strike, and swoop. These words all depict an aggressive action taken by someone or something against another person or thing, often without warning. They can be used in a variety of contexts, such as describing military tactics, animal behavior, or even figuratively in terms of seizing opportunities. Each synonym has its own nuances and connotations, but they all convey a sense of sudden, forceful action.