Not wearing or protected by armor; unarmored and vulnerable to attack or harm.
From armor (from Old French 'armure') plus the suffix -less (meaning without). The word emerged in English to describe warriors or soldiers without protective gear.
Medieval knights feared being 'armorless' in battle because even a padded tunic wouldn't stop a sword—this is why armor technology became so important that entire economies were built around smithing and metalwork.
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