1. expresses that something is unsuitable, inappropriate, or not in accordance with proper standards or etiquette
It is improper that you speak to your elders in that manner.
É impróprio que você fale com seus mais velhos daquela forma.
2. indicates disapproval of an action or behavior as being against social norms or conventions
It is improper that she attends the formal dinner without proper attire.
É impróprio que ela compareça ao jantar formal sem roupas adequadas.