'Sibi nocet' is a Latin phrase that translates to 'it harms himself' or 'he harms himself,' using the reflexive pronoun 'sibi' to indicate that the subject is affected by their own actions. This expression highlights the importance of reflexive pronouns in showing how the subject interacts with or impacts themselves in a given context. Understanding this term requires a grasp of how reflexive pronouns function to indicate actions directed back at the doer, which is key to mastering Latin sentence structures.