1. A means of networking that makes use of the Internet for private, encrypted communication. Extranets are often used to link two or more intranets. From Linux Guide @FirstLinux

2. An intranet that is accesible to computers that are not hysically part of a companys' own private network, but that is not accessible to the general public, for example to allow vendors and business partners to access a company web site. Often an intranet will make use of a Virtual Private Network. (VPN.) From Matisse