Piercing

"Piercing" is the UDEized word for Trample (as used in MTG, etc). Pierce is the word used in the Yu-Gi-Oh! Video Games, and the effect is characterised by the following text in the card lore:

During battle between this attacking card and a Defense Position monster whose DEF is lower than the ATK of this card, inflict the difference as Battle Damage to your opponent.

OR

This card inflicts Piercing damage.

The following monsters automatically have Piercing:

• Airknight Parshath
• Ancient Gear Golem
• Bitelon
• Cyberdark Horn
• Cyber End Dragon
• Dark Driceratops
• Elemental Hero Bladedge
• Elemental Hero Darkbright
• Elemental Hero Plasma Vice
• Enraged Battle Ox
• Evil Hero Inferno Wing
• Evil Hero Malicious Edge
• Gaia Soul the Combustible Collective
• Gravekeeper's Spear Soldier
• Gyaku-Gire Panda
• Mad Sword Beast
• Majestic Mech - Goryu
• Mefist the Infernal General
• Neo-Parshath, the Sky Paladin
• Ocean's Keeper
• Phantom Beast Wild-Horn
• Saber Beetle
• Spear Dragon
• Sphinx Telea
• Super Vehicroid Jumbo Drill

Other monsters can have the "Piercing" ability activated, , usually through a cost (such as a reduction in ATK) or by a Summoning option. These include:

• Ancient Gear Gadjiltron Dragon (must be Tribute Summoned with "Green Gadget" as one of the Tributes)
• Exarion Universe (ATK reduced by 400)
• Familiar-Possessed - Aussa (must be Special Summoned by its own effect)
• Familiar-Possessed - Eria (must be Special Summoned by its own effect)
• Familiar-Possessed - Hiita (must be Special Summoned by its own effect)
• Familiar-Possessed - Wynn (must be Special Summoned by its own effect)
• Koitsu (must be equipped to "Aitsu" as a Union Monster by its own effect)
• Pitch-Dark Dragon (must be equipped to "Dark Blade" as a Union Monster by its own effect)
• Super-Electromagnetic Voltech Dragon (must be Tribute Summoned by Tributing "Batteryman C")

Also, some Spell and Trap Cards can give Piercing to one or more monster(s) on the field. These include:

• Big Bang Shot (Equip Spell Card)
• Cyclon Laser (Equip Spell Card; can only equip to "Gradius")
• Dragon's Rage (Continuous Trap Card; gives all Dragon-Type monsters Piercing)
• Fairy Meteor Crush (Equip Spell Card)
• H - Heated Heart (Normal Spell Card)
• Meteorain (Normal Trap Card)
• Strike Slash (Normal Trap Card)
• Spiral Spear Strike (Continuous Spell Card; gives "Gaia the Fierce Knight", "Swift Gaia the Fierce Knight", and/or "Gaia the Dragon Champion" Piercing)

An interesting side-effect of Equip Spell Cards that give Piercing, is that you can inflict damage to your opponent by equipping them to your opponent's monster(s). Then, when your opponent attacks one of your Defense Position monsters with an ATK greater than your monsters DEF, he/she will take the difference. After all, even though it's your opponent's monster, it's your Spell Card, and thus it's your opponent — not you — who takes the extra damage.