Wiktionary
helideck
n. (context nautical English) A platform (on a vessel or offshore structure) on which helicopters may land and take off.
Usage examples of "helideck".
Every gun was trained on it now, as it came within 20 feet of the helideck at the rear of the ship.
Above the helideck on the ship was the same sort of UFO thing that had hovered briefly over the hangar in Berlin.