A scratching post was an object made for cats to scratch.
In 2370, after having borrowed Spot briefly, Geordi La Forge complained to Data that she had ruined one of his chairs by using it as a scratching post. (TNG: "Force of Nature")
In 2380, T'Ana told Beckett Mariner she looked like a scratching post when she declined to have her scars removed. (LD: "Temporal Edict")