Which formation in Football is called the Christmas tree formation?

Answer 1

Milan actually plays in 4-3-2-1
In Italy we call this tactic "formazione ad albero di natale"
This was their line-up in one 'serie a' match:
Milan (4-3-2-1): 12 Dida;
(4) 2 Cafu, 13 Nesta, 3 Maldini, 4 Kaladze;
(3) - defensive mids 8 Gattuso, 21 Pirlo, 20 Seedorf;
(2) - offensive mids 22 Kakà, 10 Rui Costa;
(1) 7 Shevchenko.
(77 Abbiati, 14 Simic, 19 Costacurta, 5 Redondo, 23 Ambrosini, 15 Tomasson, 18 Borriello). All. Carlo Ancelotti.

Answer 2

If by football you mean soccer to us americans then its a variation of the 4-4-2 which is a highly effecting formation