off grounds; outside the premises
Refers to areas outside a defined facility or compound, often used in contrast with 構内 (on the premises).
Smoking is prohibited outside the premises.
There is a parking lot off the grounds.
構外 means the area outside a facility's boundaries, the direct opposite of 構内, which means inside those boundaries.
Compound of 構 (こう, 'structure, premises') and 外 (がい, 'outside').