"Heads" (or "the head") is the nautical term for a toilet or bathroom on a boat. Historically located in the bow ("head") of the ship, this placement allowed seawater to wash away waste and odors, as this Youtube video notes, it was also designed to prevent odors from drifting aft.

Key Details Regarding "Heads" in Sailing:
Location History: The name originates from old sailing ships where the crew's toilet facilities were placed in the front (the "head" of the ship) to keep the living areas cleaner.

Modern Usage: On modern yachts, the "head" refers to the marine toilet/bathroom facility, whether it is a small cabinet or a dedicated room, according to Sunsail.

Alternative Definition: "Head" can also refer specifically to the top corner of a triangular sail, as American Sailing explains.