The place that supports the bottom of the mast. The mast step usually has a built in pattern fitting a matching pattern on the bottom of the mast, enabling the mast to be accurately positioned.
the thing that the bottom of the mast sits on, either at the bottom of the boat or on the deck. If the mast has stays, the mast step has to take a lot of downward thrust.
A mortise cut into the top of a keelson or large floor timber, or a mortised wooden block or assembly of blocks mounted on the floor timbers or keelson into which the tenoned heel of a mast was seated.