Sarcasm is a form of verbal irony where someone says something but means the opposite, often in a mocking or contemptuous way. It is often used to convey disdain or to criticize someone or something in a humorous fashion. For example, if someone performs poorly in a task and another person says, "Great job!" with a tone that suggests the opposite, that is sarcasm.
The word "sarcasm" comes from the Greek word "sarkasmos," which is derived from "sarkazein," meaning "to tear flesh." This reflects the biting nature of sarcasm, as it can be hurtful or cutting in tone.