Definition of SLD (Second-Level Domain)

The portion of an Internet address that identifies the specific and unique administrative owner associated with an IP address. The second-level domain name includes the TLD (top-level domain) name. For example, in ecommerce-dictionary.com, "ecommerce-dictionary" is a second-level domain. "ecommerce-dictionary.com" is a second-level domain name (and includes the top-level domain name of "com").