In the game of Go
), "table shape" refers to the arrangement of stones shown here:
It is a good, strong shape, made from an iron pillar, a keima and an ikken tobi. Like the bamboo joint, it cannot be cut apart, but because the base is wider, it is a bit lighter, and more flexible. However, in the absence of significant opposing strength in the vicinity, it is overconcentrated. Therefore, it is most common to see this shape arise along the boundary between two players' areas of influence, and especially when there are stones of the opponent's at the points marked a and b.
As far as I know, there is in fact no "official" name for this shape, but "table shape" is what someone on Sensei's Library decided to call it, and it's common enough that it deserves its own name.