If someone is obstinate, they are very stubborn and don't want to change their mind.
Being obstinate is usually seen as a bad thing because it can make it hard to work with that person.
Examples:
She is so obstinate, she won't listen to anyone.
The obstinate child refused to eat his vegetables.
The obstinate dog wouldn't move from the doorway.
The obstinate cat refused to play with the new toy.
He was so obstinate, he wouldn't even try the delicious cake.
The obstinate mule wouldn't budge no matter how much they pulled.