an undefined situation or subject that does not seem to conform to known categories or rules; an intermediate area or topic that is not clearly defined
Idioms and Phrases with gray area
gray area
Indeterminate territory, undefined position, neither here nor there. For example, There's a large gray area between what is legal and what is not. This term, which uses gray in the sense of “neither black nor white” (or halfway between the two), dates only from the mid-1900s.