Tank

From HGWiki

A tank is a particular role one or more party members fill during combat. The primary purpose of a tank is to prevent enemy mobs from attacking other characters, especially the squishies. As such, tanks must be able to withstand damage and debilitating effects, and also must be mobile to chase down anything that gets passed them. Damage output it secondary to tanking.

For more info one the gaming term, see http://en.wikipedia.org/wiki/Tank_(gaming)