Louw-Nida Greek and English Lexicon Based on Semantic Domains defines ἀσέλγεια (in the NT) this way:
"behavior completely lacking in moral restraint, usually with the implication of sexual licentiousness - 'licentious behavior, extreme immorality.'"
L-N then lists 2 Cor. 12:21 and offers these comments:
"In some languages the equivalent of 'licentious behavior' would be 'to live like a dog' or 'to act like a goat' or 'to be a rooster,' in each instance pertaining to promiscuous sexual behavior" (Semantic Domain 88.272).
One who practices ἀσέλγεια is reckless in his/her conduct. Such an individual evidently has little regard for what God or men think (Eph. 4:19).