deponent

n. [ L. deponenes, -entis, laying down. See Depone, v. t. ] 1. (Law) One who deposes or testifies under oath; one who gives evidence; usually, one who testifies in writing. [ 1913 Webster ]

2. (Gr. & Lat. Gram.) A deponent verb.

Syn. -- Deponent, Affiant. These are legal terms describing a person who makes a written declaration under oath, with a view to establish certain facts. An affiant is one who makes an affidavit, or declaration under oath, in order to establish the truth of what he says. A deponenet is one who makes a deposition, or gives written testimony under oath, to be used in the trial of some case before a court of justice. See under Deposition. [ 1913 Webster ]