The phrase "acting corporal" refers to a temporary promotion to the rank of corporal within the military or law enforcement. Some synonyms for this term include temporary corporal, stand-in corporal, interim corporal, and substitute corporal. These terms all refer to someone who is filling in temporarily for a corporal who is temporarily unavailable or who has been promoted to a higher rank. While the term "acting" implies that the person is only temporarily in the role, it is still important to recognize and respect the authority and responsibilities that come with the rank of corporal.