Capable of being enclosed or able to be shut in or surrounded.
From enclose + -able (suffix forming adjectives meaning capable of); enclose comes from en- + close, from Old French 'clos' meaning shut.
Though not commonly used, 'enclosable' appears in technical or legal documents when describing areas that can potentially be fenced in or sealed—it's the adjective form of possibility.
Complete word intelligence in one call. Free tier — 50 lookups/day.