a piece of paper that can be used to get something without paying for it, or at a reduced price:
If you collect ten coupons from the newspaper, you can get a free beach towel.
UK a piece of paper, especially a part of an advertisement in a newspaper or magazine, that a reader can send to an organization in order to get information about its products or services:
To find out more about our products, fill in the coupon and send it to us at the address given below.