Definition of Virtual machine:
A computer system created using software on one physical computer in order to emulate the functionality of another separate physical computer.
Software that mimics the actions of a CPU, or other hardware devices, in utilizing a computers resources and resides as a protected memory space, usually on a hard disk. For example, in the context of a Java Virtual Machine, it executes Java applets in a web browser. Whereas different computer platforms may require different JVMs (due to differing operating systems) they all can execute Java code irrespective of the source program (the browser) being used.
Meaning of Virtual machine & Virtual machine Definition