Improper activities are illegal or dishonest.
25 officers were investigated following allegations of improper conduct.
25名警官被指控有非法行为而受到调查。
Improper conditions or methods of treatment are not suitable or good enough for a particular purpose.
The improper use of medicine could lead to severe adverse reactions.
用药不当会引起严重的不良反应。
If you describe someone's behaviour as improper, you mean it is rude or shocking or in some way socially unacceptable.
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。