Definition of "open-source"

open-source

adjective
not comparable
1. (software) Of or relating to a product which is licensed to permit modifications and redistribution of its source code, as per The Open Source Definition.
  Quotations
  ASP.NET MVC has been under an open-source license since the initial release, but it was just open-source code instead of a full open-source project.
  2014, Jon Galloway, Brad Wilson, K. Scott Allen, David Matson, Professional ASP.NET MVC 5, John Wiley & Sons, page 10
2. (by extension) Describing any product whose composition or method of manufacturing is public knowledge and not proprietary.
3. (espionage) Relying on publicly available information (open sources).
verb
third-person singular simple present open-sources, present participle open-sourcing, simple past and past participle open-sourced
1. (transitive) To release the source code of.
  Quotations
  The big Unix company Sun Microsystems bought the code for StarOffice in 1999, and some time afterward they open-sourced as much of it as they could.
  2005, David Brickner, Test Driving Linux: From Windows to Linux in 60 Seconds