NetBSD is a free, secure, and highly portable, UNIX-like operating system available for many platforms, from 64-bit AlphaServers and desktop systems to handheld and embedded devices. Its clean design and advanced features make it excellent in both production and research environments, and it is user-supported with complete source.
A free variant of Berkeley UNIX available for Alpha, x86, 68xx, PA-RISC, SPARC, PowerPC, ARM, and many other types of machines. Its emphasis is on portability.
This term refers to free BSD Unix version that is focused on portability.