engastration, n. The stuffing of one animal inside another, before presenting it for dinner.
The obvious modern (American) example is turducken (turkey stuffed with a duck stuffed with a chicken); I gather that the English equivalent replaces the turkey with a goose.
Etymology: from Greek gaster, abdomen. Although the culinary concept has been around for thousands of years, this term seems to have originated in the early 1800s. I see some more relaxed uses of the word in the late twentieth century (a "philosophic engastration", engastrating a text into one's own, etc.).
Some more examples of engastration gleaned from Google:
A 13th century Andalusian cookbook includes a recipe for "the complete" or "the inclusive", a ram stuffed with assorted cooked birds filled with a breadcrumb stuffing; the stuffed ram is rubbed with spices and oil and cooked in a clay oven.
Trojan boar, a boar stuffed with birds, was apparently a popular food at Roman feasts.
The Invasive Species Cookbook: Conservation Through Gastronomy has a recipe for wild boar stuffed with Chinese mitten crab.