noun, noun which may take the genitive case particle 'no'
outside the building; off the premises
Used for areas outside a specific facility such as a library, museum, or hall. Often appears in signs or rules.
Please refrain from eating and drinking outside the building.
This material cannot be checked out of the library.
館外 means outside the building (e.g. 館外貸出, taking a library book off the premises), the direct opposite of 館内.
Compound of 館 (kan, 'building, hall') and 外 (gai, 'outside').