罪过 is a noun with two main clusters of meaning. The literal sense refers to a fault, sin, or offense (often in a moral or religious context). In polite social interaction, it functions as a humble expression — when someone compliments you or gives you a gift, you can say 罪过罪过 to mean 'I don't deserve this' or 'you're too kind'. It can also be used as a polite apology for a minor mistake, similar to 'excuse me' or 'my fault'. The word is often reduplicated as 罪过罪过 in these formulaic uses.