大娘 is used to politely address a woman roughly your mother's age or older - warm and rural-flavored, strongest in northern/northeastern China. Compare
阿姨 (āyí), which is the more urban, universal 'auntie'. Using
大娘 on a woman under ~50 in the city can accidentally age her; stick to
阿姨 if you're in Shanghai or Guangzhou.
