Refers to a person, weapon, or vehicle which has a high output, but a low defense, life, durability, etc.
The Blaster (City of Heroes), dex zon (Diablo 2),golf glub (Silent Hill 4),and Red Gazelle (F-Zero GX) are glass cannons.
Game Term. Refers to a class of vehicle or sometimes a unit that has very high attack strength and sometimes long range but generally poor defense and low health as a result.
The general strategy for them is to either destroy the enemy before being attacked or hides behind other, stronger ally units.
The artillery unit in that game is great. But it's a Glass Cannon, I only use it for defense.
A build of an Amazon in Diablo II, which has low life and defense but makes up in the fields of insane damage and speed with a bow.
You basically stack Dex instead of Vit, and instant damage.
Your goal is usually a 7 frame attack.
Fred: Woah, did you see Bill's new Glass Cannon? That mother fucker owned all the little hoes in that pub game!
John: He stole my gold :(
Fred: Shut up John, you little bitch.
In the context of an (MMO)RPG:
1. Usually refers to the casting classes, i.e. the ones that rely on magic instead of melee.
2. Generally the term applies to any character class that delivers more attack damage than, yet will nevertheless lose in a 1 vs 1 fight to, some standard garden-variety warrior.
Kiting is a glass cannon's best friend.
Warrior1: Dude, I just killed like 10 wizards, woot.
Warrior2: SFW dude, they're glass cannons, and they had already used up all their spells.