Definition
This idiom suggests that when visiting or living in a new place, one should adapt to and follow the local customs and practices.
In that small town, all the shops closed after lunchtime, so we had to when in Rome and wait until the afternoon to go shopping.
Although I don't usually like spicy food, now that I'm here, I'll when in Rome and try the local specialties.
In that culture, people usually take off their shoes before entering a house, so we decided to when in Rome.