Thanks for asking a question on www.thisisyourbible.com
The word lasciviousness means to be given over to the desires of the flesh.
Here's how Vine's dictionary of New Testament words puts it:
aselgeia (G766) denotes "excess, licentiousness, absence of restraint, indecency, wantonness"; "lasciviousness" in Mar_7:22, one of the evils that proceed from the heart; in 2Co_12:21, one of the evils of which some in the church at Corinth had been guilty; in Gal_5:19, classed among the works of the flesh; in Eph_4:19, among the sins of the unregenerate who are "past feeling"; so in 1Pe_4:3; in Jud_1:4, of that into which the grace of God had been turned by ungodly men; it is translated "wantonness" in Rom_13:13, one of the sins against which believers are warned; in 2Pe_2:2, according to the best mss., "lascivious (doings)," RV (the KJV "pernicious ways" follows those texts which have apoleiais); in 2Pe_2:7, RV, "lascivious (life)," KJV, "filthy (conversation)," of the people of Sodom and Gomorrah; in 2Pe_2:18, RV, "lasciviousness" (KJV, "wantonness"), practiced by the same persons as mentioned in Jude. The prominent idea is shameless conduct.
I hope you have found this helpful.