the GNU version of the Collaborative International Dictionary of English
n. One who, or that which, confirms, establishes, or ratifies; one who corroborates.
The Century Dictionary and Cyclopedia
n. One who or that which confirms, establishes, or ratifies; one who produces corroborative evidence; one who or that which verifies or corroborates; an attester.
Word Usage
"Afin d'ajuster de prévoir le nombre de repas en alimentation vivante, nous vous remercions de nous confirmer votre participation jeudi 19 février au plus tard."