TURKEY, n. A large bird whose flesh when eaten on certain religious anniversaries has the peculiar property of attesting piety and gratitude. Incidentally, it is pretty good eating.
2009 Update: A creature that, by domestication, caging and overfeeding has evolved from a wild fowl into a symbol for American gratitude and ambition. The turkey retains enough power of flight to avoid a "flightless" description but not enough to avoid a recipe.
Happy Thanksgiving to all Americans, foreign and domestic.