If someone is stroppier, they are more likely to get angry or upset.
Being stroppier is not a good thing. It can make people not want to be around you.
Examples:
She is getting stroppier because she is tired.
He is stroppier than his sister.
The cat is getting stroppier because it's hungry.
The dog gets stroppier when it doesn't get its dinner.
My little brother gets stroppier than anyone when he's hungry.
The baby gets stroppier when it's sleepy.