What is the definition of mail order brides?

Most people think of a mail order bride as a woman a man can literally purchase for marriage. In the past, men could order women from a catalog and have her shipped to his home. However, traditional mail order brides no longer exist, at least in first-world countries. Today, people confuse the women on Russian dating sites as mail order brides, but these women are not for sale. They're just women interested in dating foreign men.