Posttraumatic stress disorder (PTSD) is a psychiatric condition that can develop following an extremely traumatic event (such as a sexual assault, car accident, mugging, combat, or any other traumatic event). According to the Diagnostic and Statistical Manual of Mental Disorders, a person may be diagnosed with PTSD if he experiences certain symptoms (such as nightmares about the event, avoidance of things that remind the person of the event, irritability, feeling constantly alert or on guard) after exposure to a trauma.
Read more about posttraumatic stress disorder from About.coms Guide to PTSD.

