I'm not native so maybe that's the reason I understand this wrong and so I'm not the perfect person for rewording the docs ;-) I can try but I'm not satisfied:

> For every key in the array returns all documents (possibly none) matching that key. Documents order matches keys order.

Maybe you can find some inspiration in [couchdb docs](http://docs.couchdb.org/en/latest/api/database/bulk-api.html)