"An imaginary computer that runs compiled Java programs. Your computer or Web browser must emulate a virtual machine to run a Java applet or application." (Greg Perry, "Sams Teach Yourself Beginning Programming in 24 Hours" 2nd Ed., 2001)
"The combination of hardware and software (OS, DBMS, etc.) that provides the underlying environment that supports the operation of a software product." (Richard D Stutzke, "Estimating Software-Intensive Systems: Projects, Products, and Processes", 2005)
"Everything under the control of a guest operating system that is managed by a Hypervisor." (David G Hill, "Data Protection: Governance, Risk Management, and Compliance", 2009)
"System that offers the expected functionality associated with a device, but is actually implemented on top of a lower level system. The typical example is the Java Virtual Machine, which specifies a mode of operation for a virtual processor that is subsequently emulated on a different processor architecture." (Max Domeika, "Software Development for Embedded Multi-core Systems", 2011)
"software that allows you to take a single physical device (e.g., one PC) and run multiple instances of operating systems on it." (Bill Holtsnider & Brian D Jaffe, "IT Manager's Handbook" 3rd Ed., 2012)
"A computer operating system and associated storage and input/output resources that are completely provided by software. This is done by a hypervisor that allocates hardware resources by translating between the actual hardware and the software that attempts to access it. See also hypervisor." (Mark Rhodes-Ousley, "Information Security: The Complete Reference" 2nd Ed., 2013)
"Software programs that look and run like a physical computer." (Weiss, "Auditing IT Infrastructures for Compliance" 2nd Ed, 2015)
"The illusion created by a timesharing system that each user has a dedicated machine" (Nell Dale & John Lewis, "Computer Science Illuminated" 6th Ed., 2015)
"This term is ambiguous. (a) It sometimes refers to the combination of the system hardware resources and the low-level operating system (called a hypervisor) that is responsible for creating the illusion to operating systems running on it that they have exclusive use of the system. (b) A virtual machine can also refer to a guest operating system running on top of a hypervisor." (O Sami Saydjari, "Engineering Trustworthy Systems: Get Cybersecurity Design Right the First Time", 2018)
"A virtual machine is a software representation of a computer." (Alex Thomas, "Natural Language Processing with Spark NLP", 2020)
"An IBM mainframe operating system that can host other IBM operating systems such as MVS or VSE, so that an application running under an operating system seems to have its own complete system of software and hardware resources." (Microfocus
"The software implementation of a physical computer that runs an operating system. Multiple virtual machines can run simultaneously on the same hardware. In Azure, virtual machines are available in a variety of sizes." (Microsoft, "Azure Glossary")
