helmet
n. countablen. a hard hat that you wear to protect your head from injury. You use it when riding a bike, playing sports, or working in dangerous places.
n. a protective head covering made of hard material, designed to prevent injury from impact or falling objects.
Always wear a helmet when you ride your bicycle.
The construction workers are required to wear a safety helmet at all times while on the site.
Modern racing helmets are engineered from lightweight carbon fiber to provide maximum impact resistance without compromising the driver's neck mobility during high-speed maneuvers.
From Middle English helmet, helmett, a borrowing from Old French helmet, heaumet, a diminutive of helme (Modern French heaume), equivalent to helm + -et. The Old French is itself of Germanic origin (whence Old English helm). Used in English since the 15th century, it has largely displaced helm as the general word.
Commonly used with the verb 'wear' or 'strap on'.