virtual

adj. being such in power or effect though not formally recognized; imaginary, hypothetical; computer simulated

n. computerized representation of an actual object (Computers)

The term virtual is a concept applied in many fields with somewhat differing connotations, and also, differing denotations. Colloquially, 'virtual' has a similar meaning to '-' or 'pseudo-' (prefixes which themselves have quite different meanings), meaning something that is almost something else, particularly when used in the adverbial form e.g., "He's virtually [almost] my boyfriend". The term recently has been defined philosophically as, that which is not real, but may display the full qualities of the real.
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adj. virtual, being such in power or effect though not formally recognized; computer simulated

adj. constructive; potential, virtual

(a.)
Having the power of acting or of invisible efficacy without the agency of the material or sensible part; potential; energizing.
  

(a.)
Being in essence or effect, not in fact; as, the virtual presence of a man in his agent or substitute.