Definition of "plinth"

There appears to be no definite information about the origin of the two large boulders, mounted on plinths, on the platforms of St. Anne's Park Station, Bristol.

1948 July and August, “The Why and The Wherefore: Boulders at St Anne's Park Station”, in Railway Magazine, page 280

He turned back to the scene before him and the enormous new block of council dwellings. The design was some way after Corbusier but the block was built up on plinths and resembled an Atlantic liner swimming diagonally across the site.

1963, Margery Allingham, “Foreword”, in The China Governess‎