WordReference Random House Unabridged Dictionary of American English © 2020
crash hel′met, 
  • Automotivea helmet for protecting the head in the event of an accident, worn by motorcyclists, automobile racers, etc.
    • 1915–20

    Collins Concise English Dictionary © HarperCollins Publishers::
    crash helmet n
    1. a padded helmet worn for motorcycling, flying, bobsleighing, etc, to protect the head in a crash
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