It's the bottom of a building or a building. Base of a sculpture, a pedestal, statue or a column. Rodapié or lower frieze of a wall. It is another way to call the floor of the seabed, also called Continental Shelf or Underwater Platform. In Geology primary layer (basal) that is, it belongs to the Paleozoic or Primary Era.
* Only one "like" per meaning and day, the more "likes" the meaning will appear higher in the list