The act of attesting or certifying as a witness or officially.
- Nuttall's Standard dictionary of the English language. By Nuttall, P.Austin. Published 1914. (noun) (n.) (noun)
The act of certifying; testimony given on oath, or by official declaration.
- The Winston Simplified Dictionary. By William Dodge Lewis, Edgar Arthur Singer. Published 1919. (noun) (n.) (noun)
The act of bearing witness to; putting a name to a writing in order to show it to be authentic.
- Etymological and pronouncing dictionary of the English language. By Stormonth, James, Phelp, P. H. Published 1874. (noun) (n.) (noun)
Act of attesting.
- The american dictionary of the english language. By Daniel Lyons. Published 1899. (noun) (n.) (noun)
The act of attesting; testimony.
- The Clarendon dictionary. By William Hand Browne, Samuel Stehman Haldeman. Published 1894. (noun) (n.) (noun)

Usage examples:

But this fresh attestation of the canon is subject to the same inconveniences with those traditions of the ancient persons that I defend, and whom Irenaeus both heard and saw; for it is equally distant from the original, and could not be made except by such only as had reached those remote times.
- The Grounds of Christianity Examined by Comparing The New Testament with the Old by George Bethune English
And, in truth, an excessive display of outward honor would seem to be the most uncertain attestation of the real affection of a people for any king or potentate.
- Plutarch-Lives-of-the-noble-Grecians-and-Romans by Clough, Arthur Hugh
The penalties attached to a " false answer on attestation were heavy, as he knew, and he would take no chances.
- Servants of the Guns by Jeffery E. Jeffery