The act of having a Ménage à trois while the woman is dressed as a Pilgrim or Indian Squaw. One guy is in the process of receiving a blumpkin, while the other is in the process of giving the woman a cream pie.
The first Blumpkin Pie.
While Miles Standish was in the outhouse (after the first Thanksgiving), the hot redheaded pilgrim girl started to give him a blumpkin. John Smith came by and was so aroused that he joined in and gave her a cream pie.