This can also be seen as a phase before menstruation where the woman enjoys cuddling and snuggling more than usual.
Heather: Why do you think that?
Barbera: Because shes nesting.
i.e. a bed pushed against a wall with a window for smoking, internet access, porn, toilet paper, beer fridge, TV/DVD, game console, beer fridge, hash pipe, etc.
roommate B: "oh, that must be Tanya. She can't go unless she's nesting."
Group nesting is called a Nest Fest.
This act can lead to Burrowing. Burrowing can lead to babies.
Sam- "What a nesting whore."