1. Existing or resulting in essence or effect though not in actual fact, form, or name: the virtual extinction of the buffalo.
2. Existing in the mind, especially as a product of the imagination. Used in literary criticism of a text.
3. Computer Science Created, simulated, or carried on by means of a computer or computer network: virtual conversations in a chatroom.

Usage Note: When virtual was first introduced in the computational sense, it applied to things simulated by the computer, like virtual memory—that is, memory that is not actually built into the processor. Over time, though, the adjective has been applied to things that really exist and are created or carried on by means of computers. Virtual conversations are conversations that take place over computer networks, and virtual communities are genuine social groups that assemble around the use of e-mail, webpages, and other networked resources. · The adjectives virtual and digital and the prefixes e- and cyber- are all used in various ways to denote things, activities, and organizations that are realized or carried out chiefly in an electronic medium. There is considerable overlap in the use of these items: people may speak either of virtual communities or of cybercommunities and of e-cash or cybercash. To a certain extent the choice of one or another of these is a matter of use or convention (or in some cases, of finding an unregistered brand name). But there are certain tendencies. Digital is the most comprehensive of the words, and can be used for almost any device or activity that makes use of or is based on computer technology, such as a digital camera or a digital network. Virtual tends to be used in reference to things that mimic their "real" equivalents. Thus a digital library would be simply a library that involves information technology, whether a brick-and-mortar library equipped with networked computers or a library that exists exclusively in electronic form, whereas a virtual library could only be the latter of these. The prefix e- is generally preferred when speaking of the commercial applications of the Web, as in e-commerce, e-cash, and e-business, whereas cyber- tends to be used when speaking of the computer or of networks from a broader cultural point of view, as in cybersex, cyberchurch, and cyberspace. But like everything else in this field, such usages are evolving rapidly, and it would be rash to try to predict how these expressions will be used in the future.