endorse

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

• transitive verb To express approval of or give support to, especially by public statement; sanction.
• transitive verb To recommend (a product), often in exchange for payment, as in an advertisement.
• transitive verb To write one's signature on the back of (a check) to obtain the amount payable or to make the amount payable available to a third party or to the bearer.
• transitive verb To write one's signature on the back of (an instrument) to transfer the rights available under that instrument to another party.
• transitive verb To place (one's signature), as on a contract, to indicate approval of its contents or terms.
• transitive verb To acknowledge (receipt of payment) by signing a bill, draft, or other instrument.

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

• noun (Her.) A subordinary, resembling the pale, but of one fourth its width (according to some writers, one eighth).
• transitive verb Same as indorse.

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

• verb To support, to back, to give one's approval to, especially officially or by signature.
• verb To write one's signature on the back of a cheque, or other negotiable instrument, when transferring it to a third party, or cashing it.
• verb To give an endorsement.
• noun heraldry A diminutive of the pale, usually appearing in pairs on either side of a pale.

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

• verb give support or one's approval to
• verb guarantee as meeting a certain standard
• verb sign as evidence of legal transfer
• verb be behind; approve of