Other forms: gray areas
A gray area is a situation that's unclear or open to interpretation. The sign on the door of the cafe clearly states dogs aren't allowed — whether you can bring your pet goat inside is a gray area.
Something that's a gray area is ambiguous — in other words, it's not clearly stated or doesn't fit neatly into a set of rules or a category. Certain laws need to be reworked after they're written if there are gray areas, or situations that haven't been accounted for. Some documents include gray areas that are essentially loopholes that allow people to avoid an obligation like paying taxes. "Writing off my laptop as a business expense is a gray area."