Such improper behaviour and language from a young lady left me momentarily incapable of speech.

如此不得体的言行竟来自一位年轻女士，这让我惊愕得一时无语。

《柯林斯英汉双解大词典》

But it also stipulates that improper behaviour that flouts local customs may lead to fines, prosecution or deportation.

但它同时又规定任何藐视地方习俗的不恰当行为都可能导致罚款，遭到诉讼或被驱逐出境。

youdao

Her own behaviour had been so very improper!

她自己的行为也很不检点呀！

youdao

But the difference for Cardinal O'Brien is that he is accused of improper behaviour himself.

BBC: Cardinal O'Brien's departure leaves a rudderless Church

The men accused the Scottish Catholic Church leader of improper behaviour in the 1980s - allegations he contests.

BBC: UK

In fact, one suspects that the police would have regarded accusations of such improper behaviour as domestic or trivial.

BBC: Jimmy Savile and workplace culture today