The Collaborative International Dictionary of English v.0.48:
Brood \Brood\ (br[=o]ch), v. i. [imp. & p. p. Brooded; p. pr.
& vb. n. Brooding.]
1. 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.
2. 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.