Seudah HaMafseket is the "separating meal" eaten before the fasts of Yom Kippur and Tisha B'Av.
At the pre-Tisha B'Av meal it is forbidden to eat meat (Mishna, Taanit 26b; Babylonian Talmud ibid. 30a), wine, and fish, or more than one cooked food. Alcoholic beverages should be avoided. The meal is eaten sitting on the ground or a low seat. It is customary to eat a hardboiled egg, and also a piece of bread dipped into ashes, and to say, "This is the Tisha B'Av meal." During the meal, three men should not sit together so they will not have to recite the Grace after Meals as a group. None of these restrictions apply when the eve of Tisha B'Av falls on the Sabbath.
The pre-Yom Kippur meal is a festive meal, which may include meat.
Read more about this topic: Seudat Mitzvah