D defs.my
Entry 4 senses Webster, 1913

Helmet

/hĕl'-mət/ · Hel·met · IPA /ˈhɛlmɪt/
01 n. A defensive covering for the head. See Casque, Headpiece, Morion, Sallet, and Illust. of Beaver.
  1. 1.
    A defensive covering for the head. See Casque, Headpiece, Morion, Sallet, and Illust. of Beaver.(Armor) See: Casque, Headpiece, Morion, Sallet, Beaver
  2. 2.
    The representation of a helmet over shields or coats of arms, denoting gradations of rank by modifications of form.(Her.)
  3. 3.
    A helmet-shaped hat, made of cork, felt, metal, or other suitable material, worn as part of the uniform of soldiers, firemen, etc., also worn in hot countries as a protection from the heat of the sun.
  4. 4.
    That which resembles a helmet in form, position, etc.(Chem.)
Phrases & compounds
Helmet beetle — a leaf-eating beetle of the family Chrysomelidae, having a short, broad, and flattened body. Many species are known.
Helmet shell — one of many species of tropical marine univalve shells belonging to Cassis and allied genera. Many of them are large and handsome; several are used for cutting as cameos, and hence are called cameo shells. See King conch.
Helmet shrike — an African wood shrike of the genus Prionodon, having a large crest.