A DFA, or "Death From Above" (not to be confused with a Katas or Lunges) is a special move initiated by pressing forward, jump and attack at once. They tend to restrict the player's movement, making them open to attacks, but do a large amount of damage.
Generally when referring to "DFA" with no further description, this is the move being referred to. The player leaps forward striking the ground with his saber dealing very high damage, usually enough to instantly kill a player. When used accurately, its high damage and swiftness makes it a good counter attack against other slow special moves, making it Red's only effective counter attack. Its' long cool down period leaves the player very exposed, so it should usually only be used when you are certain it will kill the target.
Also known as YDFA, the player leaps upwards into the air in a flip, and attacks below him. This attack is notable due to the server remaining active (still dealing attack dammage) whilst it is being held still at the end of the attack. This quirk can be used to deal large amounts of damage via exploits.
In singleplayer, there are two versions of this DFA.
Staff and Dual Butterfly
With staff or dual, the same combo causes the player to begin a multiple hit combo in which they travel forwards spinning around. These moves can also be done to the left and right. There is a limited amount of control over which direction the player moves in, by turning with the mouse, but the direction is locked for parts of the move.
Staff Reverse DFA
By pushing back instead of forward with the staff, you can perform a backflip move.