The Greek adjective asebes (ἀσεβής) means "ungodly, impious, without reverence for God" — used both as an adjective and as a substantive (the ungodly person). It is derived from the alpha-privative a- and sebomai (to worship with reverence). The term describes persons who actively lack godly reverence.
In Romans 5:6, Paul makes one of the most radical statements of the gospel: "At just the right time, when we were still powerless, Christ died for the ungodly (asebon)." The ungodly — those actively without reverence for God — are precisely whom Christ died to redeem. This is grace in its most scandalous form. 1 Peter 4:18, quoting Proverbs 11:31, asks: "If it is hard for the righteous to be saved, what will become of the ungodly and the sinner?" The rhetorical force drives urgency toward repentance. In Jude, asebes characterizes the false teachers who have crept into the church — those whose apparent godliness is a mask.