Sleeve gun and wrist gun are generic terms for a small firearm designed to be concealed under a long-sleevedcoat or jacket—in fictional examples there is often a device with a mechanism to extend it out into the hand to fire.
Though designs vary, most fictional sleeve guns involve a small conventional pistol on a sliding or telescoping rail, which quickly releases the weapon into the hand for firing, either by a trigger mechanism, or just the sudden movement of the forearm. Such sleeve guns have appeared in multiplemedia.