A rigid device, where a submissive is attached, for the purpose of exposing them, to be whipped, without risk to their limbs and to insure a clear striking surface.
In ancient times, the most common whipping post, was simply a strong post, which an offender was shackled or manacled to.
Today's modern posts, are generally crosses, either straight or made into an "X" shape, which is the preferred variation.
The "X" shaped whipping post, has a variety of uses, but when used in Whipping or Flagellation scenes, it stretches the arms and legs, out of the way, further improving the striking surface.
Additionally, they are slightly bent, to allow the subject to rest on them, and further keep the limbs out of the way.
Usually cuffs are used for restraints, in that they wrists and ankles are firmly affixed to the far end of each cross piece, restricting movement of the limbs, adding to the experience.