Designated for Assignment (DFA)
Sometimes a club wants to remove a player from its MLB Reserve List (40-man roster), but it has to be done immediately because the player's roster slot is needed, and it takes two business days to get a player through waivers. Or sometimes a club wants to remove a player from its MLB Active List (25-man roster), but the player has no minor league options remaining (or would have to clear Optional Assignment Waivers before he can be optioned to the minors), so the only way to remove the player from the 25-man roster would be by Outright Release, Outright Assignment, or a trade (or in the case of a player who needs to clear Optional Assignment Waivers before he can be optioned to the minors, only after Optional Assignment Waivers have been secured). In those cases, a club can place a player on the Designated List.
When a player is placed on the Designated List (and is "Designated for Assignment"), the "Designated Player" is removed from his club's MLB Reserve List (40-man roster), and then the club has up to ten days to either trade, release, or outright the player to the minors. A club can also return a Designated Player to the 40-man roster and either option the player to the minors or reinstate the player to the 25-man roster, as long as the Designated Player is not replaced on the 40-man roster by another player while the player is on the Designated List. (A club might have to DFA a player to buy time while it attempts to secure Optional Assignment Waivers).
A player continues to be paid and continues to accrue MLB Service Time while on the Designated List.
Also, a player acquired off waivers can be placed back onto Outright Waivers by his new club and can be outrighted to the minors if he is not claimed, but if a club acquires a player off waivers and the claiming club's 40-man roster is full so that the club needs to remove a player from its MLB Reserve List in order to open a spot on its 40-man roster for the newly-acquired player, the player who was claimed off waivers cannot be the player who gets "Designated for Assignment."