A standard round of golf has only eighteen holes. The 19th hole is a code term typically for a pub, bar or restaurant on or near the golf course, very often the clubhouse itself. Golfer will say they are at the ‘19th hole,’ meaning they are getting a drink after the round.
For a while, Volcano House was advertising golf with a unique 19th hole. “The nineteenth hole of Kilauea golf course at Hilo, Hawai‘i, provides the worst golfer in the world a chance to record his hole-in-one. It is the Halemaʻumaʻu fire-pit of Kilauea volcano and is half a mile wide and 1200 feet deep.”