名詞 helmet:

1. armor plate that protects the head
2. a protective headgear made of hard material to resist blows

1. A cloth band or scarf wrapped around the crown of a hat or sun helmet.
   頭巾纏繞在禮帽或遮陽帽帽冠周圍的布條或三角巾
2. A medieval light helmet with a neck guard and movable visor.
   頭盔中世紀(jì)有護(hù)頸和活動(dòng)護(hù)面的輕便頭盔
3. Jerry: I never had a beard. I kept my hair inside the helmet.
   杰端：我以前是從不留胡子，我頭發(fā)是在頭盔里。
4. These policemen wear helmets to protect them.
   這些警察戴著頭盔保護(hù)自己。

hel.met

n.（名詞）

A head covering of hard material, such as leather, metal, or plastic, worn by football players, firefighters, construction workers, motorcyclists, and others to protect the head.
頭盔：由堅(jiān)硬材料如皮革、金屬或塑料制成的頭部覆蓋物，由橄欖球隊(duì)員、消防隊(duì)員、建筑工人、摩托車騎手或其他人配戴，用以保護(hù)頭部
The headgear with a glass mask worn by deep-sea divers.
（潛水）頭盔：由深水潛水員戴的帶有玻璃面罩的帽盔
A pith helmet; a topi.
遮陽帽：干木髓做的太陽帽；軟木帽
A head covering, such as a balaclava, that is shaped like a helmet.
帽盔：一種形狀象頭盔的頭部覆蓋物，如巴拉克拉瓦盔式帽
A piece of armor, usually made of metal, designed to protect the head.
盔甲：一件盔甲，通常由金屬制成，設(shè)計(jì)用于保護(hù)頭部
Botany The hood-shaped sepal or corolla of some flowers.
【植物學(xué)】 盔狀花冠（或花萼）：某些花朵盔狀的花萼或花冠
v.tr.intr.（及物動(dòng)詞和不及物動(dòng)詞）
hel.met.ed,hel.met.ing,hel.mets
To provide with or put on a helmet.
給…提供（或配戴）頭盔

來源：
Middle English
中古英語
from Old French [diminutive of] helme
源自 古法語 [] helme的小后綴
[of Germanic origin] * see kel-
[日爾曼語源的] *參見 kel-

【引伸】
hel.meted
adj.（形容詞）