A dead body; a corpse.

a magic wielder who has managed to extend his live by unnatural means until he/she/it becomes undead

an evil magic-user or cleric who, through ultra-powerful magic, has made himself undead

an undead spellcaster, usually a wizard or sorcerer but sometimes a cleric or other spellcaster, who has used its magical powers to unnaturally extend its life

a powerful sorcerer who has survived death

a powerful undead horror, the twisted remains of a wizard or sorcerer who completed a dark magic ritual as an attempt to gain immortality

a spell caster who seeks to defy death by magical means

In modern fantasy fiction, a lich (sometimes spelled liche, and pronounced 'litch') is a type of undead creature, usually an evil magician or a powerful undead king. The use of the term lich as a specific type of undead creature originates in the Dungeons & Dragons role-playing game; previous works of fantasy fiction, such as Clark Ashton Smith's "Empire of the Necromancers", had used it as a general term for any animated or inanimate corpse. Liches often control other undead, using them as their soldiers and servants.

In the Dungeons & Dragons fantasy role-playing game, the lich is an undead creature; a spellcaster who seeks to defy death by magical means.