Shock is medical condition where insufficient blood flow reaches the body tissues. It is can often be caused by extreme stress, or a recent traumatic incident.
In 2268, Dr. Leonard McCoy noted that Captain Krik of the USS Enterprise went into shock after being attacked by Mugato. McCoy's treatment was to keep the Captain warm until Tyree returned. (TOS: "A Private Little War").
In 2370, Garak went into a state of extreme shock aboard Deep Space 9 while recanting a horrifying (but at least partially false) story about interrogating young Bajorans during the occupation and his subsequent exile from Cardassia. (DS9: "The Wire")