Trailer phrase

• "In space no one can hear you scream," for "Alien"
• "Just do it" for Nike
• Something funny in setting of gelatin
• Identifying phrase
• "She walked off the street, into his life and stole his heart," for "Pretty Woman"
• Entertainer's signature
• "One man's struggle to take it easy," for "Ferris Bueller"
• "Just when you thought it was safe to go back in the water," e.g

Douglas Harper's Etymology Dictionary Word definitions in Douglas Harper's Etymology Dictionary
"punchline of a joke," 1926, originally "last line in an actor's speech" (1916), from tag (n.1) + line (n.).

Wikipedia Word definitions in Wikipedia
In entertainment , a tagline (alternatively spelled tag line ) is a short text which serves to clarify a thought for, or is designed with a form of, dramatic effect . Many tagline slogans are reiterated phrases associated with an individual , social group ...