Post-traumatic stress: An anxiety disorder that develops in some individuals who have had major traumatic experiences. The person is typically numb at first but later has symptoms including depression, excessive irritability, guilt (for having survived while others died), recurrent nightmares, flashbacks to the traumatic scene, and overreactions to sudden noises.
Post-traumatic stress became known in the 70s due to the adjustment problems of some Vietnam veterans. It was first listed as a diagnostic category by the American Psychiatric Association in 1980. Although the name "post-traumatic stress" was new, the condition was not. It was known as "shell shock" in World War I and "battle fatigue" during World War II.