Stalking means following someone or watching them a lot, usually because you like them or want to hurt them.
Stalking is scary and can be dangerous. It's not okay to stalk someone.
Examples:
He is stalking her.
Stalking is against the law.
She is scared because of the stalking.
The cat is stalking the bird.
The stalking went on for months.
Stop stalking me, it's not nice!