What is Affiant?

Legal Definition
The person who makes and subscribes an affidavit. The word is used, in this sense, interchangeably with "deponent" But the latter term should be reserved as the designation of one who makes a deposition.
-- Black's Law Dictionary
Legal Definition
The author of an affidavit, who swears to its accuracy.
Legal Definition
The maker of an affidavit or deposition.
-- Ballentine's Law Dictionary