Wilfully, Willfully - Vine's Expository Dictionary of New Testament Words
Wilfully, Willfully
[ A-1,Adverb,G1596, hekousios ]denotes voluntarily, willingly," Hebrews 10:26, (of sinning) "willfully;" in 1 Peter 5:2, "willingly" (of exercising oversight over the flock of God).
[ B-1,Verb,G2309, thelo ]
"to will," used in the present participle in 2 Peter 3:5, is rendered "willfully (forget)" in the RV, AV, "willingly (are ignorant of)," lit., "this escapes them (i.e., their notice) willing (i.e. of their own will)." See WILL, C, No. 1, WILLING, B, No. 1.