Through intense training you've learned how to wield even the mightiest of weapons in one hand. Though the weight may make it a bit hard to swing there's no doubt that having a spare hand will come in handy.

All two-handed weapons gain the Versatile trait. When you wield a two-handed weapon in one hand this way they gain a -3 to hit penalty on attack rolls. The weapon's damage is unaffected by this feat.
Versatile  - You can switch between using this weapon in one or two hands.