flagstone

noun

Etymology: From flag + stone.

1. A flat, rectangular piece of rock or stone used for paving or roofing.

   “Grass sprouted between the pebbles and a greenish stain lay upon the flagstones.”

   “In 1946, several of the heavy flagstones, which form the decking of the viaduct, were replaced or reseated, and manholes were provided in the decking, to facilitate access to the inner walls.”

2. One of several types of rock easily split and suitable for making flagstones.