The term "serious injury" is a legal definition that refers to any physical harm or impairment caused by an accident, which results in long-term damage or disability. This can include injuries such as broken bones, burns, lacerations, amputations, and internal injuries. The severity of the injury determines whether it is considered "serious" under the law. In some cases, a minor injury may be classified as serious if it results in significant pain or disability for an extended period of time.