headstone Meaning, Definition & Usage

  1. noun the central building block at the top of an arch or vault
    keystone; key.
  2. noun a stone that is used to mark a grave
    gravestone; tombstone.

WordNet

Head"stone` noun
Definitions
  1. The principal stone in a foundation; the chief or corner stone. Ps. cxviii. 22.
  2. The stone at the head of a grave.

Webster 1913