† affiˈdationObs.rare—1. [ad.med.L. affīdātiōn-em, f.affīdā-re: see affidavit and -tion.] A solemn promise of fidelity. 1613Daniel Hist.Eng. 62 The Empresse swore, and made affidation to the Legat..The same oath and affidation tooke likewise her brother.1755in Johnson.