What is the answer to "___ 1 (speed of sound)" in the NYT Crossword?

The answer to the NYT Crossword clue "___ 1 (speed of sound)" is MACH (4 letters).

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NYT

___ 1 (speed of sound) NYT Crossword Clue

Down clue · from the December 1, 2025 puzzle

Stuck on “___ 1 (speed of sound)” from the New York Times Crossword? Here is the verified answer:

Answer

MACH

4 letters · Down · last seen December 1, 2025