If someone tries to reactivate your account

When you deactivate your account, you can reactivate it again by logging in. We'll then send you a confirmation email to make sure you wanted to reactivate. 

If you got an "Pinterest Account Reactivation" email and you didn't try to reactivate your account, then someone else knows your Pinterest password

You should reset your password to protect your account. Don't worry, resetting your password won't reactivate your account.