The Collaborative International Dictionary of English v.0.48:

authentication \authentication\ n.
   a mark on an article of trade to indicate its origin and
   authenticity.

   Syn: hallmark, assay-mark.
        [WordNet 1.5]

   2. validating the authenticity of something or someone.

   Syn: certification.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

authentication
    n 1: a mark on an article of trade to indicate its origin and
         authenticity [syn: authentication, hallmark, assay-
         mark]
    2: validating the authenticity of something or someone [syn:
       authentication, certification]

The Free On-line Dictionary of Computing (30 December 2018):

authentication

    The verification of the identity of a person or
   process.  In a communication system, authentication verifies
   that messages really come from their stated source, like the
   signature on a (paper) letter.  The most common form of
   authentication is typing a user name (which may be widely
   known or easily guessable) and a corresponding password that
   is presumed to be known only to the individual being
   authenticated.  Another form of authentication is
   biometrics.

   (2007-02-22)


Bouvier's Law Dictionary, Revised 6th Ed (1856):

AUTHENTICATION, practice. An attestation made by a proper officer, by which
he certifies that a record is in due form of law, and that the person who
certifies it is the officer appointed by law to do so.
     2. The Constitution of the U. S., art. 4, s. 1, declares, "Full faith
and credit shall be given in each state to the public acts, records and
judicial proceedings of every other state. And congress may by general laws
prescribe the manner in which such acts,, records and proceedings shall be
proved, and the effect thereof." The object of the authentication is to
supply all other proof of the record. The laws of the United States have
provided a mode of authentication of public records and office papers; these
acts are here transcribed.
     3. By the Act of May 26, 1790, it is provided, "That the act of the
legislatures of the several states shall be authenticated by having the seal
of their respective states affixed thereto: That the records and judicial
proceedings of the courts of any state shall be proved or admitted, in any
other court within the United States, by the attestation of the clerk, and
the seal of the court annexed, if there be a seal, together with a
certificate of the judge, chief justice or presiding magistrate, as the case
may be, that the said attestation is in due form. And the said records and
judicial proceedings, authenticated as aforesaid, shall have such faith and
credit given to them, in every court within the United States, as they have,
by law or usage, in the courts of the state from whence the said records
are, or shall be taken."
     4. The above act having provided only for one species of record, it was
necessary to pass the Act of March 27, 1804, to provide for other cases. By
this act it is enacted, Sec. 1.  "That, from and after the passage of this
act, all records and exemplifications of office books, which are or may be
kept in any public office of any state, not appertaining to a court, shall
be proved or admitted in any other court or office in any other state, by
the attestation of the keeper of the said records or books, and the seal of
his office thereto annexed, if there be a seal, together with a certificate
of the presiding justice of the court of the county or district, as the case
may be, in which such office is or may be kept or of the governor, the
secretary of state, the chancellor or the keeper of the great seal of the
state, that the said attestation is in due form, and by the proper officer
and the said certificate, if given by the presiding justice of a court,
shall be further authenticated by the clerk or prothonotary of the said
court, who shall certify, under his hand and the seal of his office, that
the said presiding justice is duly commissioned and qualified; or if the
said certificate be given by the; governor, the secretary of state, the
chancellor or keeper of the great seal, it shall be under the great seal of
the state in which the said certificate is made. And the said records and
exemplifications, authenticated as aforesaid, shall have such faith and
credit given to them in every court and office within the United States, as
they have by law or usage in the courts or offices of the state from whence
the same are or shall be taken."
     5.-2. That all the provisions of this act, and the act to which this
is, a supplement, shall apply, as well to the public acts, records, office
books, judicial proceedings, courts, and offices of the respective
territories of the United States, and countries subject to the jurisdiction
of the United States, as to the public acts, records, office books, judicial
proceedings, courts and offices of the several states."
     6. The Act of May 8, 1792, s. 12, provides: That all the records and
proceedings of the court of appeals, heretofore appointed, previous to the
adoption of the present constitution, shall be deposited in the office of
the clerk of the supreme court of the United States, who is hereby
authorized and directed to give copies of all such records and proceedings,
to any person requiring and paying for the same, in like manner as copies of
the records and other proceedings of the said court are by law directed to
be given; which copies shall have like faith and credit as all other
proceedings of the said court."
     7. By authentication is also understood whatever act is done either by
the party or some other person with a view of causing an instrument to be
known and identified as for example, the acknowledgment of a deed by the
grantor; the attesting a deed by witnesses. 2 Benth. on Ev. 449.