Learner's definition of STUBBORN
[more stubborn; most stubborn]
refusing to change your ideas or to stop doing something
She's wrong, but she's too stubborn to admit it.
I admire his stubborn refusal to quit.
She has a stubborn streak. [=she is often stubborn]
He's (as) stubborn as a mule. [=he's very/extremely stubborn]
difficult to deal with, remove, etc.