What does "breech" mean?

Additional senses

1. 2.The hinder part of anything; esp., the part of a cannon, or other firearm, behind the chamber.
2. 3.(Naut.) The external angle of knee timber, the inside of which is called the throat.
3. 4.To put into, or clothe with, breeches. A great man . . . anxious to know whether the blacksmith's youngest boy was breeched. Macaulay.
4. 5.To cover as with breeches. [Poetic] Their daggers unmannerly breeched with gore. Shak.
5. 6.To fit or furnish with a breech; as, to breech a gun.
6. 7.To whip on the breech. [Obs.] Had not a courteous serving man conveyed me away, whilst he went to fetch whips, I think, in my conscience, he would have breeched me. Old Play.
7. 8.To fasten with breeching.