What is Armiger?

Legal Definition
In heraldry, an armiger is a person entitled to use a heraldic achievement (e.g., bear arms, an "armour-bearer") either by hereditary right, grant, matriculation, or assumption of arms. Such a person is said to be armigerous.
-- Wikipedia
Legal Definition
An armor-bearer; an esquire. A title of dignity belonging to gentlemen authorized to bear arms. Cowell. In its earlier meaning, a servant who carried the arms of a knight. Spelman. A tenant by scutage; a servant or valet; applied, also, to the higher servants in convents. Spelman.
-- Black's Law Dictionary
Legal Definition
A squire; one entitled to bear arms.
-- Ballentine's Law Dictionary