Rushing forward without restraint.
Precipitous.
Reckless, impetuous.
Plunging downwards head foremost.
To precipitate.
With an unrestrained forward motion.
Rashly; precipitately; without deliberation; in haste, hastily.
With the head first or down.
An aircraft that can travel at the speed of sound.
Ultrasonic, having a frequency too high to be audible.
Greater than the speed of sound (in the same medium, and at the same temperature and pressure).