Def 1: In traditional english parlance:
Simply a body or corpse of any kind.
Def 2: In some fantasy literature and role-playing game contexts:
A powerful magician who has prolonged his mortal existence beyond natural life (ie. "undeath") and is immune to many human weaknesses.
They bore the farmer's lich through the church gate for burial.
Example of play:
Game Master: Climbing from the sarcofogus you see a somewhat dessicated and decayed form, clad in the vestments of the old Karbanthi order of wizards.
Player 1: Crap! It must be a lich. I told you we shouldn't have come down this far into the dungeon.
Player 2: No problem, my character is a cleric. I cast holy smite on this undead. *player rolls dice* I rolled a 12.
Game Master: *checks lich stats, grins evily* The lich grins and bellows in a distant, echoing voice, "Foolish mortals. I am not some simple zombie your gods can knock down. You stand before Kworzathash greatest of the Karbanthi... and I will eat your souls for disturbing my work.
*deadly combat ensues*
In death, wizards of great power are sometimes able to turn themselves into liches. A lich is a skeletal, undead creature, whose magical powers can only be matched by its malevolence. The process of becoming a lich is very painful, but those who are powerful enough to become liches willingly undergo it: Liches are totally immune to any sort of mental attack, poisons, diseases and suchlike. They can also channel magical energy much easier than humans or any of the normal races, making them deadly adversaries. Liches are often seen leading great masses of lesser, undead warriors.
What exampe am I supposed to give?!
A relatively strong spellcaster in the WArcraft Custom Game, DOTA. He is a ice spellcaster. He is able to slow and damage an enemy hero with his frost nova ( Killsteal with this would be excellent ^^ )He also increase the team survivility with his spell frost armor. ( Holy Crap! +12 armors?? WTF )His dark rithual ais able to deny an allied creep for your own mana. ( So it will taunt yours foe angrily and he couldn't wait to pwn you so hard! XD! )His ultimate spell, chain frost is very powerful. ( Multiple frost nova only, duh?? )His ulti could rip his foe's living crap out of their heaven. Holy Shit!
Killmahai1256 (Lich): Ok, let check the ulti.
Killmahai1255 just pwned x hero's head for 210 golds.
Killmahai just drew first bloods! (+200 golds)
Killmahai1255 just pwned y hero's head for 210 golds!
Killmahai1256 just got Double Kill!
Killmahai1255 just pwned z hero's head for 210 golds!
Killmahai1256 is on killing spree!
Killmahai1256 just got Triple Kill!
Killmahai1256 (Lich): hahaha!
A powerful, skeletal, undead creature who casts spells to defend itself. In life, a lich was a powerful spellcaster. When it becomes a lich it is now an unholy creature whos power in casting spells is amplified into a veritable killing machine, via its majicks.
The lich only pointed at his enemy. A beam of dark energy exploded out of his finger and hit the fighter in the chest. He died on the spot.
Geek #1: Hey did you see that lich in World of Warcraft?
Geek #2: Yeah man, she was a total bitch. She was hot though.
Navid: You guys sicken me..