Armor (referred to as Armored in some card text) is a keyword effect in Bloons Card Storm. When a Bloon with Armor takes damage from any source, it is reduced by the amount of Armor it has. If a source of damage is less than or equal to a Bloon's Armor, that Bloon takes zero damage. Shields are not affected by Armor.
Some Bloons have Armor by default. Certain cards can apply Armor to other Bloons. The amount of Armor on a Bloon is indicated by a white number on an icon of a metallic plate.
None of the playable Heroes are able to gain Armor, but Dreadbloon can give itself Armor by using its Armored card.
Armor-Piercing MOAB Mauler targeting a Lead Bloon. If it attacks, it will remove all of this Bloon's Armor before dealing 65 damage.
Armor Piercing (formatted as Armor-Piercing in some card text) is a keyword effect that causes a Monkey to strip all Armor from a target Bloon or Boss Bloon before calculating and applying damage, even if it has a Shield or is immune to damage (e.g. Dreadbloon using Immunity), and regardless of ATK (e.g. Buddy Bloon's 0 ATK debuff). Of the Monkeys that have Armor Piercing, some have additional effects associated with Armor Piercing, such as the Lead to Gold Monkey.
Splash Damage not counting for Armor Piercing