This is the 9347th most frequent French word.
demeurée
"Demeurée" means "mentally impaired" or "slow-witted" in English.
Here, 'demeurée' functions as a past participle meaning 'stayed' or 'remained'.
Elle est demeurée à la maison tout l'après-midi.
She stayed at home all afternoon.
In this sentence, 'demeurée' indicates something persisting or remaining within an abstract location, in this case, the mind.
Cette idée est demeurée dans mon esprit bien longtemps.
This idea remained in my mind for a very long time.
Here, 'demeurée' describes a state of persistence, that the lamp remains unchanged in its condition of being broken.