Sarcasm is a sharp and often satirical or ironic attack designed to cause harm, either mental or social, and intended to insult or wound. It is often a mode of satirical wit depending for its effect on bitter, caustic, and often ironic language and is usually directed against an individual. 
There is a thin dividing line between sarcasm and irony.
Recently, scientists have located parts of the brain used to comprehend sarcasm . The research demonstrates that some people have difficulty distinguishing between normal speech and sarcasm.
- ↑ http://www.m-w.com/dictionary/sarcasm
- ↑ http://news.bbc.co.uk/1/hi/health/4566319.stm
- ↑ "Damage to any of three different areas could render individuals unable to understand sarcastic comments." http://news.bbc.co.uk/1/hi/health/4566319.stm