helmet

Từ điển Oxford Advanced Learner 8th

hel·met [helmet helmets helmeted helmeting] BrE [ˈhelmɪt] NAmE [ˈhelmɪt] noun
a type of hard hat that protects the head, worn, for example, by a police officer, a soldier or a person playing some sports
see also ↑crash helmet

Word Origin:
late Middle English: from Old French, diminutive of helme, of Germanic origin.

Example Bank:
•Police in riot helmets lined the streets.
•A protective helmet should be worn at all times.
•It is illegal to ride a motorcycle without a crash helmet.