What does "brood" mean?

Additional senses

1. 2.The young from the same dam, whether produced at the same time or not; young children of the same mother, especially if nearly of the same age; offspring; progeny; as, a woman with a brood of children. The lion roars and gluts his tawny brood. Wordsworth.
2. 3.That which is bred or produced; breed; species. Flocks of the airy brood, (Cranes, geese or long-necked swans). Chapman.
3. 4.(Mining) Heavy waste in tin and copper ores. To sit on brood, to ponder. [Poetic] Shak.
4. 5.Sitting or inclined to sit on eggs.
5. 6.Kept for breeding from; as, a brood mare; brood stock; having young; as, a brood sow.
6. 7.To sit on and cover eggs, as a fowl, for the purpose of warming them and hatching the young; or to sit over and cover young, as a hen her chickens, in order to warm and protect them; hence, to sit quietly, as if brooding. Birds of calm sir brooding on the charmed wave. Milton.
7. 8.To have the mind dwell continuously or moodily on a subject; to think long and anxiously; to be in a state of gloomy, serious thought; -- usually followed by over or on; as, to brood over misfortunes. Brooding on unprofitable gold. Dryden. Brooding over all these matters, the mother felt like one who has evoked a spirit. Hawthorne. When with downcast eyes we muse and brood. Tennyson.
8. 9.To sit over, cover, and cherish; as, a hen broods her chickens.
9. 10.To cherish with care. [R.]
10. 11.To think anxiously or moodily upon. You'll sit and brood your sorrows on a throne. Dryden.