'Out, out brief candle!' is a famous line from Shakespeare's play Macbeth, spoken by the character Macbeth in Act 5, Scene 5. This phrase symbolizes the fleeting nature of life and the inevitability of death. It reflects Macbeth's profound despair and realization of the futility of existence following the death of Lady Macbeth. The metaphor of a candle being extinguished highlights themes of mortality and the transient quality of human life, which are central to many of Shakespeare's works.