[men-tuh n-yair; French mahn-taw-nyer]
noun, plural men·ton·nières [men-tuh n-yairz; French mahn-taw-nyer] /ˌmɛn tənˈyɛərz; French mɑ̃ tɔˈnyɛr/. Armor.
  1. any of various plate pieces for protecting the lower part of the face, as a beaver.

Origin of mentonnière

1815–25; < French, equivalent to menton chin + -ière, feminine of -ier -ier2; see brassiere Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018