At-will; you completely avoid a melee attack. Must exceed attacker's hit check with your Parry check. Requirements: attack must be a melee attack, must come from front arc, requires awareness, cannot block touch or incorporeal attacks (except, for latter, if using force weapon).
On a successful parry, if you beat the enemy's attack by 5 or more, you may attempt to disarm; your enemy must win an opposed check (Str or Dex, as per each weapon), or his weapon is disarmed.
On a successful Parry, you may take an immediate melee attack against your attacker. The attack may be any standard or swift action you would normally use for attack.