( saying ) used to say that when you are in a foreign country, or a situation you are not familiar with, you should behave in the way that the people around you behave
WHEN IN ROME (DO AS THE ROMANS DO)
Meaning of WHEN IN ROME (DO AS THE ROMANS DO) in English
Oxford Advanced Learner's English Dictionary. Оксфордский английский словарь для изучающик язык на продвинутом уровне. 2005