A balaclava (type of headgear).

A mining helmet, a hard hat worn by miners that usually carries a light on the front. / Eggcorn of pith helmet.

(historical) A bronze helmet of Ancient Greek origin, covering the head and neck, with slits for the eyes and mouth.

(UK, uncountable) The invasive plant Impatiens glandulifera. / Used other than figuratively or idiomatically: see policeman, helmet.

plural of helmeted friarbird

A species of friarbird, Philemon buceroides, of eastern Indonesia, New Guinea, and northern Australia.

Synonym of kettle hat

Dated form of crash helmet.

(idiomatic) An accidental messy hairdo resulting from the wearing of a helmet.

plural of helmet hair