transonic

[ tran-son-ik ]
/ trænˈsɒn ɪk /

adjective Chiefly Aeronautics.

close to the speed of propagation of sound; moving at 700–780 miles per hour (1127–1255 km/h) at sea level.
Also transsonic.

Origin of transonic

First recorded in 1940–45; trans- + sonic

British Dictionary definitions for transonic

transonic
/ (trænˈsɒnɪk) /

adjective

of or relating to conditions when travelling at or near the speed of sound

Scientific definitions for transonic

transonic
[ trăn-sŏnĭk ]

Relating to or capable of speeds at or near the speed of sound (at or approaching Mach 1) or to aerodynamic conditions for bodies travelling at such speeds. Compare hypersonic subsonic supersonic.