The phrase "accompanying adult" means that there must be a grown-up person who is with or near someone, usually a child, to provide guidance and ensure safety.
Sentences with «accompanying adult»
Family rooms are available in most hotels, and children stay free with accompanying adults. (travelweekly.com)
Situated next to the queen bedroom it is especially suitable for children accompanying adults. (wikiaustralia.com)
No dog walking is permitted, may accompany an adult walking dogs. (cchsshelter.com)