[′frē ‚strēm ′mäk ‚nəm·bər] (aerospace engineering) The Mach number of the total airframe (entire aircraft) as contrasted with the local Mach number of a section of the airframe.
free-stream Mach number (MFs)
The Mach number of a body measured in free stream, which is unaccelerated by the airfoil or the body's presence.