WordNet (r) 3.0 (2006):

Mach
    n 1: Austrian physicist and philosopher who introduced the Mach
         number and who founded logical positivism (1838-1916) [syn:
         Mach, Ernst Mach]

The Free On-line Dictionary of Computing (19 January 2023):

Mach

   An operating system kernel under development at
   Carnegie-Mellon University to support distributed and parallel
   computation.  Mach is designed to support computing
   environments consisting of networks of uniprocessors and
   multiprocessors.  Mach is the kernel of the OSF/1.