Wiktionary
n. A locked box with a slot for depositing coins into, usually placed in churches to accept donations for the needy.
WordNet
Usage examples of "poor box".
As a rule this chamber held the poor box of the big cathedral from which the daily donations were collected by a preoccupied priest in the service of the cathedral at six p.
He kicked viciously at the -poor box lying next to Father Juan and sent it skidding across the floor to lodge beneath a pew.
If this is how a visitor feels, treated with respect, even deference, by the screws, I don't know how I could stand a five-year sentence, and yet I've had clients who greet five years rather like a pound from the poor box.
Uncle Charley stopped to slip five sols into the poor box before he opened the front door onto the esplanade.
She's finished gypping the sisters on the price of tomatoes, and now she'll donate the surplus profit to me for the poor box.