In sailing, the term inboard refers to anything located inside the hull of the boat, towards the centerline (the middle) of the vessel, or closer to the boat compared to another object. It is the opposite of "outboard".

Key Definitions and Contexts:
Location: Objects or crew positions inside the gunwales (edges) of the boat.

Engine: An inboard motor is an engine mounted permanently inside the hull, usually driving a propeller via a shaft passing through the bottom of the boat. These are often affectionately referred to by sailors as the "iron wind".

Relative Position: If two boats are tied together, the one closer to the dock is "inboard".

"Inboard-Outboard" (I/O): A hybrid system with an engine inside the hull (inboard) but a drive unit on the outside (outboard).