rubber stamp

/ˈrʌb·ər ˈstæmp/ n [C]

Definition

› a device used for printing with raised letters, numbers, or pictures made of an elastic substance such as rubber that you cover with ink and press against a surface, or the printed letters, etc., made in this way: The guard marked my pass with a rubber stamp. › disapproving A rubber stamp is also an approval given without much thought: The mayor has a lot of power, and city counselors provide a rubber stamp.

(Definition of rubber stamp n from the Cambridge Academic Content Dictionary © Cambridge University Press)