Freudian term that describes a person who is compulsive in his orderliness, stubborn and stingy. Called "anal" because it describes the stage of psychosexual development in which the focus of pleasure is on activities relating to elimination.
Short for anal intercourse (penis in butt). That said, it's often used to mean any kind of butt play (rimming, playing with butt plugs or vibrators, etc.), in which case it's short for "anal play." You may possibly come across these related abbreviations: A/S (anal service) and A/W (anal worship), which are situationally defined.