A small apartment attached to or carved out of a nominally single-family house, ostensibly intended for occupancy by a mother-in-law or other relative, but potentially also rented out to a stranger.

A person who is in great need of something will find a way to obtain it.

(originally nautical) The storm petrel.

Alternative form of necessity is the mother of invention

(uncommon) The mother of one's children-in-law; that is, the mother-in-law of one's children, or, the mother of one spouse in relation to the parents of the other spouse; either of two or more women whose children marry each other, such as the mother of a bride vis-à-vis the mother of the groom.

(Christianity) A title of the Virgin Mary.

(blasphemous) expression of surprise, frustration, etc.

plural of co-mother-in-law

Used to express surprise, disappointment or anger.

(idiomatic) A large assortment of people.