The word stamp has several meanings:

1. To bring your foot down hard and heavily on the ground. When you're frustrated, you might stamp your foot. Horses stamp their hooves when they're nervous or bothered by flies. The sound of boots stamping on a wooden floor echoes through the room.
2. A small piece of paper you stick on an envelope to pay for mailing it. Before you can mail a letter, you need to buy a postage stamp at the post office and attach it to the upper right corner. The stamp proves you've paid for delivery. Stamps often have interesting pictures on them: famous people, historical events, or beautiful scenes. Some people collect stamps from different countries and time periods as a hobby.
3. A tool that presses a design, mark, or words onto something. A rubber stamp might print “PAID” or “APPROVED” on documents. Libraries use stamps to mark due dates inside books. When you get your hand stamped at an amusement park, it proves you've paid admission and can come back in if you leave.
4. To mark something with such a tool. Officials stamp passports when you travel between countries. A factory might stamp its logo onto the products it makes.