1. To behave very correctly and to be easily shocked by anything rude or improper. Often used showing disapproval. English = (be) prim, (be) prim and proper, (be) prissy.
2. To be easily shocked by things related to nudity or sex. English = (be) prudish.
3. To have a very strict and severe attitude towards questions of morality. English = (be) puritanical. Idiomatic English = (be) straight-laced.