Meaning of “stamp” - Learner’s Dictionary

stamp

noun [ C ] us uk /stæmp/
The price of a first-class stamp is going up.I'd like to buy some stamps, please.I've put £2 worth of stamps on the letter.You can buy stamps from the shop on the corner.He collects stamps.
PAPER also postage stamp

A2 a small, official piece of paper that you buy and stick onto a letter or parcel before you post it

MARK

a tool for putting a special ink mark on something, or the mark made by it:

a stamp in a passport
stamp of approval

official, public approval:

The president has put his stamp of approval on the proposal.

(Definition of “stamp noun” from the Cambridge Learner’s Dictionary © Cambridge University Press)