I think it basically means anything flying/driving slightly under or near the speed of sound.
Some of the racers on the Bonneville Salt Flats set most of the world land speed records (basically anything on wheels) and are trying to beat the sound barrier (Supersonic). And are very close. Those would be called Transonic.
transonic
N. Duane Melson has written: 'Vectorizable multigrid algorithms for transonic flow calculations' -- subject(s): Aerodynamics, Transonic, Algorithms, Transonic Aerodynamics 'Use of CYBER 203 and CYBER 205 computers for three-dimensional transonic flow calculations' -- subject(s): Aerodynamics, Transonic, Computer programs, Multiphase flow, Transonic Aerodynamics
Stephen S. Stahara has written: 'Operational manual for two-dimensional transonic code TSFOIL' -- subject(s): Aerodynamics, Transonic, Aerofoils, Transonic Aerodynamics, Turbulent boundary layer 'Development of a turbomachinery design optimization procedure using a multiple-parameter nonlinear perturbation method' 'A rapid perturbation procedure for determining nonlinear flow solutions' -- subject(s): Singular perturbations (Mathematics), Blades, Turbomachines, Design and construction 'Perturbation solutions for transonic flow on the blade-to-blade surface of compressor blade rows' -- subject(s): Aerodynamics, Transonic, Transonic Aerodynamics 'Operational manual for two-dimensional transonic code TSFOIL' -- subject(s): Aerodynamics, Transonic, Aerofoils, Transonic Aerodynamics, Turbulent boundary layer
Hema Sandhyarani Murty has written: 'Nonlinear aspects of transonic aeroelasticity' -- subject(s): Transonic flutter, Nonlinearity, Flutter analysis, Transonic flow, Areoelasticity, Aeroelasticity
Transonic being past the speed of sound and subsonic is below the speed of sound.
Ross W. Mohr has written: 'Mach number effects on transonic aeroelastic forces and flutter characteristics' -- subject(s): Aerodynamics, Transonic, Flutter (Aerodynamics), Transonic Aerodynamics
Actually, transonic speed is not a speed faster than that of sound. Transonic speed is approx. Equal to the speed of sound, not faster.
Frederick A. Newman has written: 'Experimental determination of aerodynamic damping in a three-syage transonic axial-flow compressor' -- subject(s): Aerodynamics, Transonic, Transonic Aerodynamics, Unsteady flow (Aerodynamics)
Trevor H. Moulden has written: 'Fundamentals of transonic flow' -- subject- s -: Transonic Aerodynamics
Aga M. Goodsell has written: 'Transonic and supersonic Euler computations of vortex-dominated flow fields about a generic fighter' -- subject(s): Aerodynamics, Supersonic, Aerodynamics, Transonic, Supersonic Aerodynamics, Transonic Aerodynamics
Charles A Farrell has written: 'Computer program for calculating full potential transonic, quasi-three-dimensional flow through a rotating turbomachinery blade row' -- subject(s): Aerodynamics, Transonic, Dynamics, Impellers, Transonic Aerodynamics
Sanford Davis has written: 'Two dimensional transonic testing with splitter plates' -- subject(s): Transonic wind tunnels