What is the definition or description of: traumatic brain injury?

You already said it: Traumatic brain injury is damage to the brain after trauma. It can be temporary or permanent depending on the severity of the trauma, patient age, and other issues such as whether the patient has had previous trauma or is taking blood thinners.

TBI: Tbi (traumatic brain injury) in brief can be graded according to the pathology. Thus, the tbi can refer to a skull fracture, blood in the space between the skull and dura, between the dura and brain, or in the brain itself. Tbi is also classified by the glascow coma score (gcs) where 15 is normal and 3 is in a coma with no movement. The gcs has some predictive value for outcomes and guides therapy.