1. to conduct oneself in an inappropriate, rude, or disruptive manner; to behave badly or impolitely
The children were ill-behaved during the class and disrupted the lesson.
As crianças comportaram-se mal durante a aula e perturbaram a lição.
2. to act in a way that violates social norms or expected standards of conduct
He was ill-behaved at the formal dinner by talking loudly and interrupting others.
Ele comportou-se mal no jantar formal falando alto e interrompendo os outros.