transonic

Adjective

 * 1) Just below, or just above, the speed of sound (0.8 < Ma < 1.2 approximately).
 * 2) Passing from subsonic to supersonic, or vice versa.
 * 3) Travelling through a fluid (commonly air) at a speed where regions of supersonic and subsonic flow coexist simultaneously over different portions of the surface of the moving object in question.

Translations

 * French:
 * Italian: