noun

• (architecture) Masonry employing flat and well-squared stone or brick, creating an appearance similar to wooden flooring.
  "The four main spans across the waterway are carried on ashlar piers founded on Memel timber piles."
• (architecture) Stone hewn and finished to create such masonry, either completely or as a facade over an earthen or rubble core.
  "And from the choir itself, where the big hoist was working, came the shouts of the men sweating at the great wheel that swung the cut stones skyward, and the men high overhead on the hurdle-walks, waiting to receive the swinging ashlars and guide them into place."
• (military, historical) A stone intended for hurling by means of a catapult or similar device.