Shake down is a term that is commonly used to describe the act of searching someone or something rigorously. It is often used in the context of law enforcement or security checks. Some synonyms for the term shake down include search, frisk, pat down, and rummage. These words are often used interchangeably depending on the context in which they are used. Other synonyms include sift, screen, examine, and scrutinize. These words convey the sense of searching for something in a thorough and meticulous way. It is important to note that while these words have similar meanings, they may differ in their connotations and usage in certain contexts.