visor; eyeshade
Refers to the brim or peak of a cap, helmet, or similar headgear that shades the eyes. Also used for standalone eyeshades.
The visor of the baseball cap blocks the sunlight.
He was wearing a helmet with a visor.
Standard kanji spelling; 眉 (eyebrow) + 庇 (eaves/visor) suggests the shape and position.
Alternate kanji spelling using 目 (eye) instead of 眉; less common but still encountered.
Kana spelling is practical when the kanji are not needed or for learners.
Compound of 眉 (まゆ, eyebrow) and 庇 (ひさし, eaves/visor), referring to a brim that shades the eyes like eaves shade a building. The reading まびさし is a rendaku form of まゆ + ひさし.