Comparative form of the adjective 'rude', meaning less polite or more impolite.
Being ruder is not a good thing. It can make people feel bad or upset.
Examples:
He is ruder than she is.
She was ruder to me than to him.
The boy was ruder than the girl.
The cat was ruder than the dog.
The elephant was ruder than the mouse.
The teacher was ruder than the student.