Clue: -- number (speed ratio)

Answer: MACH

Length: 4

---

Similar Clues:

• ___ number (speed ratio) (MACH with 4 letters)
• Sound-speed ratio number (MACH with 4 letters)
• Speed-ratio number (MACH with 4 letters)
• Lowest speedometer number (ZERO with 4 letters)
• ___ number (speed measure) (MACH with 4 letters)
• Speed-of-sound number (MACH with 4 letters)
• Speed of sound number (MACH with 4 letters)
• Like a rational number's denominator (NONZERO with 7 letters)
• Jet speed number (MACH with 4 letters)
• Sound-speed number (MACH with 4 letters)