#1596 ἑκουσίως hekousios {hek-oo-see'-ose}

 from the same as G1595; TDNT - *,221; adv

—Greek Word Study (Transliteration-Pronunciation Etymology & Grammar)

 1) voluntarily, willingly, of one's own accord
    1a) to sin wilfully as opposed to sins committed inconsiderately,
        and from ignorance or from weakness

—Thayer's (New Testament Greek-English Lexicon)

—Strong's (Greek Dictionary of the New Testament)

—NAS Exhaustive Concordance of the Bible with Hebrew-Aramaic and Greek Dictionaries

 AV - wilfully 1, willingly 1; 2

—Exhaustive Concordance (KJV Translation Frequency & Location)