postage stamp

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A small, usually adhesive label issued by a government and sold in various denominations to be affixed to items of mail as evidence of the payment of postage.

from The Century Dictionary.

• noun An official mark or stamp, either affixed to or embossed on letters, etc., sent through the mails, as evidence of the prepayment of postage. Also called post-stamp. See stamp.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A small piece of printed paper stuck on an item to be mailed, indicating that postage has been paid.
• noun figuratively, colloquial A very small area.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a small adhesive token stuck on a letter or package to indicate that that postal fees have been paid