Definition & Meaning of "flip the bird"in English

What is the origin of the phrase "flip the bird" and how is it used?

Flip the bird is a slang phrase that appeared in early 20th-century American English to describe raising the middle finger at someone as an insult or gesture of defiance. The term comes from the middle finger being seen as a "bird" or phallic symbol, and "flip" refers to the act of lifting or showing it. Historically, it was derogatory and insulting, used to express anger, contempt, or defiance. Today it remains informal and offensive, widely recognized and used in casual, confrontational, or humorous contexts rather than polite conversation.