• (n.) One who affirms or asserts. • (n.) One who affirms, instead of taking an oath.
Af·firm'ant (ăf*fẽrm' a nt) noun [ Latin affirmans , -antis , present participle See Affirm .] 1. One who affirms or asserts. 2. (Law) One who affirms, instead of taking an oath. 
One who makes affirmation instead of making oath that the evidence which he is about to give shall be the truth, as if he had been sworn. He is liable to all the pains and penalty of perjury, if he shall be guilty of wilfully and maliciously violating his affirmation.
a person who affirms.