What is Atheist?

Legal Definition
One who denies the existence of God.

2. As atheists have not any religion that can bind their consciences to speak the truth, they are excluded from being witnesses. Bull. N. P. 292; 1 Atk. 40; Gilb. Ev. 129; 1 Phil. Ev. 19. See also, Co. Litt. 6 b.; 2 Inst. 606; 3 Inst. 165; Willes, R. 451 Hawk. B. 2, c. 46, s. 148; 2 Hale's P. C. 279.
-- Bouviers Law Dictionary
Legal Definition
One who does not believe in the existence of a God. Gibson v. Insurance Co., 37 N. Y. 584; Thurston v. Whitney, 2 Cush. (Mass.) 110; Coin. v. Hllis, 10 Cush. (Mass.) 53a
-- Black's Law Dictionary
Legal Definition
One who does not believe in Gods existence.
-- Ballentine's Law Dictionary