one's regular inn; one's usual hotel
Refers to a lodging place (inn, hotel, ryokan) that one habitually stays at, often while traveling for business or on regular trips.
出張のときはいつもあの定宿に泊まる。
When on business trips, I always stay at that regular inn.
When I go to Kyoto, I already have a regular place to stay.
Standard kanji spelling; 定 conveys 'fixed/regular'.
Alternate kanji spelling; 常 also means 'usual/regular'.
Compound of 定 (じょう, 'fixed, regular') + 宿 (やど, 'inn, lodging').