A slap or "smack" is a broad stroke made with the open hand or the back of the hand, as opposed to a punch that is made with a closed fist. Slaps are frequently made across the face, but can be also made across hands or any other body part, and can use either the palm of the hand or the back of the hand.
Etymology and definitions 
The word was first recorded in 1632, probably of imitative origin (onomatopoetic). The word is found in several English colloquialisms, such as, "slap fight", "slap-happy", "slapshot", "slapstick", "slap on the wrist" (as a mild punishment), "slap in the face" (as an insult or, alternatively, as a reproof against a lewd or insulting comment), and "slap on the back" (an expression of friendship or congratulations). In music, the term is used in jazz, referring to the action of pulling strings back and allowing them to smack the instrument.
"Bitch slap" is African-American slang that dates back to the 1990s. It is used to mean killing a woman, or to refer to a woman hitting a man, or a woman or gay man haranguing somebody, or a man hitting someone else in an effeminate way. Bitch slap has also been used in American prisons since the 1990s to refer to slapping instead of punching, with the implication that the perpetrator isn't "man enough" to deliver a closed-fist punch.
For about five years beginning in 2004, happy slapping became a UK fad. Happy slapping is the phenomenon whereby kids assault someone while being taped by a friend on their mobile phone: afterwards the video is uploaded to a site like YouTube.  
The SlapperDapper is a variation of the slap, whereby one slaps using both the inside and the outside of the hand in one fluid motion. If carried out successfully, there can be no comeback. However if the recipient dodges or catches the SlapperDapper, then a free slap must be awarded. 
Usage and meaning 
The purpose of a slap is often to humiliate, more than injure. A "slap in the face" is a common idiom, dating back to the late 1800s, that means to rebuke, rebuff or insult.
In his 2004 text The Naked Woman: A Study of the Female Body, anthropologist Desmond Morris defines what he calls the "cheek slap," which he describes as "the classic action of a lady responding to the unwelcome attentions of a male." Morris categorizes the cheek slap as a display blow, meaning one that is impossible to ignore but doesn't cause much damage.
The word "slap" is frequently used to minimize the perceived violence of an act, even if the act was especially severe. One person may hit another across the face and injure him/her severely, but in calling it a slap, it may seem less severe, since slapping is often associated with minor violence.
Cultural aspects 
Slapping is viewed differently by different cultures. In Iceland, slapping of children is viewed as an extreme form of physical abuse, whereas in the United Kingdom it is seen by only some parents as abusive, and only moderately so. An Indian study found a high rate of approval for husbands slapping their wives, particularly among husbands and middle-class Indians.
Studies have shown that although Americans frown upon domestic violence regardless of whether the perpetrator is male or female, generally they are more accepting of minor violence, such as slapping, when it's perpetrated by a woman against a man rather than the opposite. This is probably because women are considered less likely than men to cause physical harm. However, women who inflict minor acts of violence on their male partners have a higher-than-normal probability of being severely assaulted by those partners, and domestic violence experts therefore advise at-risk women to refrain from even minor acts of physical aggression against their partners. Also, both men and women who are violent with their spouses are more likely to slap or spank their children as well.
United States intelligence agencies use insult slaps as a form of an enhanced interrogation technique.
In India, the insult slap is a political maneuver used to express disapproval of ideas of a particular public figure or politician.
Popular entertainment 
Slapping is very often portrayed in films and television programs. For example, in Slap Her... She's French girls and women typically slap boys, men and other females who offend them in some way and humiliate them. Such films have been criticized for helping to create a cultural acceptance of women slapping men, at least as opposed to men striking women. This acceptance of gender-based abuse has been justified by some on the basis that women are generally physiologically weaker than men and cause less harm than men when they slap.
See also 
|Look up slap in Wiktionary, the free dictionary.|
- slap, Online Etymology Dictionary
- Oxford English Dictionary
- Green, Jonathon (2005). Cassell's dictionary of slang (2. ed. ed.). London: Weidenfeld & Nicholson. p. 114. ISBN 0304366366.
- Livingstone, edited by Sonia; Haddon, Leslie (2009). Kids online: opportunities and risks for children. Bristol: Policy. p. 150. ISBN 1847424384.
- Levy, Frederick (2008). 15 minutes of fame: becoming a star in the YouTube revolution. Indianapolis, IN: Alpha. ISBN 1592577652.
- Roberts, Andrea Clifford-Poston ; foreword by Liz (2008). A playworker's guide to understanding children's behaviour : working with the 8-12 age group. London: Karnac. p. 145. ISBN 1855754940.
- Stokie Handbook - Ben Newman
- Ammer, Christine (1997). The American heritage dictionary of idioms (1st pbk. ed. ed.). Boston, Mass. [u.a.]: Houghton Mifflin. p. 589. ISBN 039572774X.
- Morris, Desmond (2007). The naked woman: a study of the female body (Reprint. ed.). New York: Thomas Dunne Books/St. Martin's Press. p. 76. ISBN 0312338538.
- Cotterill, Janet. Language in the Legal Process. Basingstoke: Palgrave Macmillan, 2004. pp. 81-82, ISBN 0-333-96902-2
- Renzetti, Claire and Raquel Bergen. Violence against Women. Lanham: Rowman & Littlefield, 2005. p. 45, ISBN 0-7425-3055-8
- Malley-Morrison, edited by Kathleen (2004). International perspectives on family violence and abuse: a cognitive ecological approach. Mahwah, N.J.: Lawrence Erlbaum. pp. 20, 36. ISBN 0805842454.
- Umar, Mohd. (1998). Bride burning in India: a socio-legal study. New Delhi: A.P.H. Publ. Corp. p. 46. ISBN 8170249228.
- Forman-Brunell, edited by Miriam; Paris, Leslie (2010). The Girls' History and Culture Reader; The Twentieth Century. Urbana: University of Illinois Press. p. 29. ISBN 0252077687.
- Berliner, edited by David; Sarró, Ramon (2009). Learning religion: anthropological approaches. New York: Berghahn Books. p. 35. ISBN 1845455940.
- Arnett, Jeffrey Jensen (2007). International encyclopedia of adolescence. New York: Routledge/Taylor & Francis. p. 492. ISBN 0415966671.
- Loseke, Donileen et.al. Current Controversies on Family Violence. Thousand Oaks: Sage Publications, 2005. pp. 66-67 ISBN 0-7619-2106-0
- Lamb, Michael. Parenting and Child Development in "Nontraditional" Families. Hillsdale: Lawrence Erlbaum Associates, 1999. p. 311 ISBN 0-8058-2748-X
- Denmark, Florence and Michele Paludi. Psychology of Women. New York: Praeger, 2008. p. 562 ISBN 0-275-99162-8