Spiritual and superstitious meaning
In Hinduism, the hand gesture is known as the "Apana yogic mudra". In Indian classical dance forms the hand gesture symbolises the Lion. In Buddhism it is seen as an apotropaic gesture very commonly used by Gautama Buddha as "Karana Mudra" which is synonymous with expulsion of demons and removal of obstacles like sickness or negative thoughts.
The apotropaic usage of the sign can also be seen in Italy and in other Mediterranean cultures where, when confronted with unfortunate events, or simply when these events are mentioned, the sign of the horns may be given to ward off bad luck. It is also used traditionally to counter or ward off the "evil eye" (malocchio in Italian). In Italy specifically, the gesture is known as the corna. With fingers pointing down, it is a common Mediterranean apotropaic gesture, by which people seek protection in unlucky situations (it is thus a more Mediterranean equivalent of knocking on wood). Thus, for example, the President of the Italian Republic, Giovanni Leone, shocked the country when, while in Naples during an outbreak of cholera, he shook the hands of patients with one hand while with the other behind his back he superstitiously made the corna, presumably to ward off the disease or in reaction to being confronted by such misfortune. This act was well documented by the journalists and photographers who were right behind him, a fact that had escaped President Leone's mind in that moment.
In Italy and other parts of the Mediterranean region, the gesture must usually be performed with the fingers tilting downward to signify the warding off of bad luck; in the same region and elsewhere, the gesture may take a different, offensive and insulting meaning if it is performed with fingers upward or if directed aggressively towards someone in a swiveling motion (see section below). In Italy, one can also "touch iron" (tocca ferro) or touch one's nose to ward off bad luck. Males in Italy may also grab their testicles when confronted by bad luck; however, this is considered more vulgar.
In Peru one says contra (against). In the Dominican Republic the expression is zafa, said against curses known as fukú. All of these gestures are meant to conjure supernatural protection.
The sign of the horns is used during religious rituals in Wicca, to invoke or represent the Horned God.