affirm 1. To confirm a judgment, as where an appellate court confirms the judgment of a court below it. 2. To make a solemn declaration instead of taking an oath (if one has no religious belief, or the taking of an oath is contrary to a religious belief). The usual form is I...do solemnly, sincerely and truly declare and affirm that the evidence which I shall give shall be the truth, the whole truth and nothing but the truth. 3. To declare with full knowledge of the facts an intention to proceed with a contract. Lapse of time may be evidence of affirmation.