Closed down is a common term that means shutting down a business permanently or temporarily. There are several similar terms that can be used instead of closed down, including shutdown, closure, cessation, halt, and termination. Shutdown refers to the sudden stopping of a business operation, whereas closure is a more formal term often used in legal or official contexts. Cease, on the other hand, means stopping or ending something gradually. Halt and termination both refer to the complete stop of a business operation, but termination often involves a more permanent stoppage. All of these terms can be used interchangeably with closed down depending on the context in which they are used.