The crude weapons of Beastmen are empowered by their bearer’s primal hatred for the trappings of civilisation.
Whilst subject to Primal Fury, a hand weapon carried by a model with this special rule has an Armour Piercing characteristic of -2.
Note that this special rule only applies to a single, non-magical hand weapon and does not apply to a model’s mount (should it have one). If the model is using two hand weapons or any other sort of weapon, this special rule ceases to apply.