A covering (for sin).
And he shall bring a ram without blemish out of the flock, with thy estimation, for a trespass offering, unto the priest: and the priest shall make an ATONEMENT for him concerning his ignorance wherein he erred and wist it not, and it shall be forgiven him. ( Leviticus 5:18 )
Bibliography Information"Entry for 'Atonement'". A King James Dictionary.