a.

1. 事實上的，實際上的，實質上的
   He is in a state of virtual slavery.

   他實際上處於一種被奴役的狀態。

2. 【物】虛的
3. 【電腦】虛擬的

adj.

1. almost or nearly as described, but not completely or according to strict definition.
2. Computing  not physically existing as such but made by software to appear to do so.
3. Optics  relating to the points at which rays would meet if produced backwards.
4. Mechanics  relating to or denoting infinitesimal displacements of a point in a system.