indorsement

from The Century Dictionary.

• noun Superscription; a noting of the contents of any paper on its back; a docketing; briefing.
• noun In law, an incidental or subsidiary writing upon the back of a paper, writing, or other document, to the contents of which it relates or pertains.
• noun More specifically In commercial law: The signature of the payee of a note, bill, or check, or that of a third person, written on the back of the note or bill in evidence of his transfer of it, or of his assuring its payment, or both.
• noun The transfer or assurance so manifested.
• noun Ratification; sanction; approval.

from the GNU version of the Collaborative International Dictionary of English.

• noun The act of writing on the back of a note, bill, or other written instrument.
• noun That which is written on the back of a note, bill, or other paper, as a name, an order for, or a receipt of, payment, or the return of an officer, etc.; a writing, usually upon the back, but sometimes on the face, of a negotiable instrument, by which the property therein is assigned and transferred.
• noun Sanction, support, or approval.
• noun See under Blank.

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

• noun Alternative spelling of endorsement.

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

• noun the act of endorsing
• noun a promotional statement (as found on the dust jackets of books)
• noun formal and explicit approval
• noun a signature that validates something
• noun a speech seconding a motion