Wiktionary
n. 1 The monastery from which the other 'houses' of a religious order or congregation were (directly or indirectly) founded, often eponymous. 2 The convent which is the seat (and often the above original foundation) of the superior of an order or congregation, and/or on which lower ranking houses (such as priories under an abbot) depend.
Wikipedia
The term motherhouse is used by religious institutes to designate the principal house or community for that group. It can be for the entire institute or a region.
It would normally be where the residence and offices of the religious superior of the institute would be located. If the institute is divided geographically, it is referred to as the provincial motherhouse and would be where the regional superior would be in residence.
Usage examples of "motherhouse".
Talamasca Motherhouse in England that the Vampire Lestat first made himself known to me.
If we had a great dinner at the Motherhouse, and we did have many, she either abstained or continued drinking on her own until she passed out.
The Motherhouse was at supper, so we had the room entirely to ourselves, with no special request.
I observed at once that not one, but two small paneled trucks had come from the Motherhouse, and that there stood guard a small group of Talamasca acolytes, ready to pack up the house.
I can see those manners in the people at the Motherhouse and I hear the way they talk.
I had come to love the New Orleans Motherhouse, and I did seek every excuse to remain.
Most of us found it very delicious, and no matter where I was in the Motherhouse, I knew, by the rise of this delightful scent, when Merrick had come through the front door.
Frequently they divide their time between the Motherhouse and a private family home.
I was driven directly to the Motherhouse, a little disturbed that neither Aaron nor Merrick had come to meet my plane.
Then I insisted we return to the Motherhouse, and Merrick, who was at that time in some sort of daze, agreed.
New Orleans Motherhouse, I dressed in my usual tweed suit and came downstairs for breakfast, with the other members assembled there.
I approached Oak Haven, the Motherhouse, to see if I could spy Merrick within.
I go to where I can see her, David, yes, near the Motherhouse, the place you long ago forbade us ever to trouble.
How many years ago was it, David, that I came to visit you in the Motherhouse in London?
But if Merrick Mayfair does not return at once to the Motherhouse called Oak Haven, we will take steps to make of you a quarry in any part of the world to which you might go.