In David Copperfield, what does superannuated mean?

Superannuated is an adjective used to describe something that is too old or worn for further work or service, or retired (especially with a pension) because of old age or infirmity. It also describes something obsolete, old-fashioned, or outdated.

In David Copperfield, little Davy is sent on a visit to the Peggotty family home:

I looked in all directions, as far as I could stare over the wilderness, and away at the sea, and away at the river, but no house could I make out. There was a black barge, or some other kind of superannuated boat, not far off, high and dry on the ground, with an iron funnel sticking out of it for a chimney and smoking very cosily; but nothing else in the way of a habitation that was visible to me.