1
general::
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.
American Heritage Idioms
2
general::
Phrase(s): a gray area
Fig. an area of a subject or question that is difficult to put into a particular category because it is not clearly defined and may have connections or associations with more than one category. • The responsibility for social studies in the college is a gray area. Several departments are involved. • Publicity is a gray area in that firm. It is shared between the marketing and design divisions.
McGrawhill's American Idioms And Phrasal Verbs