Forcemeat is a mixture of ground meat and other ingredients, bound with egg. Or, sometimes it's bound with breadcrumbs. Basically, it's meat paste.
So, pulpatoon is sort of an extra-meaty meat pie, which could be an interesting option for this week's pi day.
Etymology: Italian, from polpetonne, a large meatball or risolle. The word was in use in cookbooks at least as early as the 1700s, but does not appear to be in use today.
Similar words are poupeton and pupton. Exact distinctions between the three words are unclear.
The modern paupiette describes a very similar dish.
A recipe for apple poupeton, and one for a pulpatoon of pigeons, and very nearly the same dish as a pupton of pigeons.