Head-butt

A headbutt (French coup de tête) is a targeted strike with the head, typically (when intentional) involving the use of robust parts of the headbutter's cranium as the area of impact. The most effective headbutts strike the most sensitive areas of an opponent, such as the nose, using the stronger bones in the forehead (frontal bone) or the back of the skull (occipital or parietal bone). It can be considered a quick, very effective but risky maneuver, as a misplaced strike can cause greater injury to the person delivering the headbutt than to the person receiving it. A headbutt does not have to be against another person's head, although this is usually the nearest and easiest target.

In the United Kingdom, a headbutt is sometimes referred to as a Glasgow kiss. This is a tongue-in-cheek reference to the city of Glasgow's violent reputation.

From French botter = "to kick". Rams are well known for butting with their heads and horns. From this the terms battering ram and hydraulic ram are derived. Many males in various animal species employ butting during courtship.

Headbutts can be used from close range such as from the clinch, or on the ground. They are typically applied to the head of the opponent, since the head is often a readily available target and has several sensitive areas. An effective headbutt can be performed with a forward, rising, sideways or backwards motion; each being effective from different positions.

Parts of the cranium with thick bone and high local curvature make for good weapon areas, and these include the forehead near the hairline, the outboard curved part of the parietal bone, and the occiput. Ideal targets are usually the fragile areas of the head, including the bridge of the nose, the cheekbones, the hinge area of the jaw, the temple, and the top edge of the eye socket.

...
Wikipedia