Specifically in Christian contexts, referring to the fallen angel.
In Christianity, Lucifer is considered a fallen angel.
Extended use: a devilish or demonic figure, not necessarily the biblical Lucifer.
The morning star is also called Lucifer.
He has a devilish charm, almost like Lucifer.
明けの明星 is the plain Japanese term for the morning star (Venus), while ルシファー is a more poetic, Latin-derived name for the same phenomenon.
From English 'Lucifer', ultimately from Latin 'lucifer' meaning 'light-bringer'.