Sarcasm is the making of remarks intended to sneer, jest, or mock the person referred to (who is normally the person addressed), a situation or thing. It is often used in a humorous manner and expressed through particular vocal intonations. This is often done by simply over-emphasizing the actual statement, or particular words of it.
Because it is vocally-oriented, sarcasm is often hard to pick up in written messages and is often misinterpreted. To prevent this, sarcastic comments on the Internet are usually ended with an emoticon or surrounded with <sarcasm> .. </sarcasm> tags. (This is popular on Slashdot.)
The word comes from the late Latin word, sarcasmus, which, in turn, comes from the Greek sarkasmos, from sarkazein - to bite the lips in rage,- from sarx, sark-, flesh - the root word literally mean "to cut a piece of flesh (from the targeted person)."
It was described as "the lowest form of wit" by Oscar Wilde. In 1983, Leonard Rossiter published a book titled The Lowest Form of Wit (ISBN 0722175132) which includes the history of sarcasm, rules of sarcasm, and many sarcastic comments by notable individuals.
The term is often misused as a synonym for irony. Irony refers however to the literal meaning and the intended meaning of the words uttered being different, while sarcasm refers to the mocking intent of the utterance. It is possible to be ironic without being sarcastic, and to be sarcastic without being ironic.
Sarcasm is also often confused with cynicism, which in common use is seen as a fundamental nihilistic attitude towards other people and life, whereas sarcasm can often be seen even as a positive way of thinking about things.