The term "lumbrical" is usually used for a muscle in the hand. It is responsible for flexing the metacarpophalangeal (MCP) joint and extending the interphalangeal (IP) joints. However, there are a few different terms that can be used as synonyms for this muscle. One common synonym is "lumbrical muscle," which is used interchangeably with "lumbrical." Another synonym for the lumbrical muscle is "lymphangion," which refers to a small muscle cell that regulates the flow of lymph fluid. Additionally, the term "worm-like muscle" can be used to describe the lumbrical muscle because its shape resembles that of a worm.