noun

• (historical) A sleeveless or short-sleeved coat of mail armour (a shorter hauberk).
  "Their mightie ſtrokes their haberieons diſmayld, / And naked made each others manly ſpalles; […]"
• (historical) The quilted undergarment worn under a hauberk.
  "His quilted habergeon stuffed with cotton, gave him, indeed, an exterior almost herculean. What finally became of this brave belligerent I did not learn; but as he was never shy in exposing his person, it is very probable that[…]"
• (loosely) A hauberk, any coat of mail, less commonly even a coat of scale armour.
  "The defensive armour, or coat of mail of a knight, or man at arms, (also called a hauberk or habergeon,) was[…]"