Definition - What does Trunk mean?
A trunk, in the field of software development, is the unnamed version of a file or program that is being processed under revision control. A trunk may become highly unstable when being constantly worked on by the developers, but at the same time they are the most recent front-line version of the file.
A trunk is also known as a baseline, mainline or master of a development file.
Techopedia explains Trunk
A trunk is the base of a project which precedes the development. A common practice is to cut off a branch from the main truck process, perform development on the cut-off branch and merge it back into the trunk. In this way, the working and stable part is implemented and merged inside the project file. This helps in preserving the stability and integrity of the project. The trunk may be the least, most or moderately stable version of any file depending on the type of development and the processing in revision control. Branched development is often done in projects where the trunk is often changed and merged with the updated project version.