The term "vpn 专线" could refer to a specific service or term related to Virtual Private Networks or internet services. However, without more context, it's challenging to provide a precise definition or explanation. If you're referring to a specific service provider, it might be helpful to know which industry or platform you're interested in. For example, "vpn 专线" might be a dedicated internet service provider, a VPN service, or a specific type of internet infrastructure. If you can provide more context or clarify your question, I'd be happy to assist further!