A floor attack, commonly/officially known as a getup attack (おきあがり攻撃 or 起き上がり攻撃) or rising attack, and referred to as DownAttackU and DownAttackD (depending on which side the character is laying on) internally in Brawl files, is a form of floor recovery. When the attack button is pressed while a character lies on the ground, the character will simultaneously stand up and perform a weak attack that hits on both sides to create space.
The attack used depends on whether the character is sitting (after tripping), lying face up, or lying face down; these are respectively known in Japanese as 転倒おきあがり攻撃 or 転倒起き上がり攻撃 (Tumble over getup attack), あおむけおきあがり攻撃 or 仰向け起き上がり攻撃 (Face up getup attack) and うつぶせおきあがり攻撃 or うつ伏せ起き上がり攻撃 (Face down getup attack).
Floor attacks are seldom used as a getup option in competitive play, as their animations grant relatively low intangibility frames compared to other getup options, and the user is vulnerable to being punished if an opponent shields the attack. However, they are effective for creating space when cornered or to prevent an opponent from readying an attack.
In SSB4, floor attacks deal moderate shield damage. In the case where an opponent with a slightly-damaged shield is hit by both the front and back floor attacks, it can be enough to cause a shield break.
If the character is lying the attack does 6%, and if they're sitting the attacks does 5% unless otherwise noted.
List of back floor attacks
List of front floor attacks
List of trip floor attacks