In Webster's 1828 Dictionary (the ORIGINAL Webster's Dictionary), "wickedness" is defined as follows......
"Departure from the rules of the divine law; evil disposition or practices; immorality; crime; sin; sinfulness; corrupt manners Wickedness generally signifies evil practices. But wickedness expresses also the corrupt dispositions of the heart."
So, yes....Atheism, by definition, is wickedness; but, a Christian, who does not walk in Love (Matthew 22:37-40), is also guilty of wickedness ("corrupt dispositions of the heart").