Slayer is an elite melee military dwarf obtained by upgrading a Berserker dwarf. The slayer sacrifices armor for a very high damage output.

It is a final form military dwarf.

It's possible that the Slayer is a reference to the Dwarven Slayers of Warhammer Fantasy fame, as they are typically seen as bare chested dwarven warriors with a mohawk and with a weapon in each hand.