Definition of orthopinacoid in US English:

orthopinacoid

(also orthopinakoid)

noun

  • In a monoclinic crystal: a plane parallel to the vertical axis and the orthodiagonal axis.

Origin

Mid 19th century; earliest use found in James Nicol (1810–1879), geologist. From ortho- + ancient Greek πινακ-, πίναξ pinax + -oid.

Pronunciation

orthopinacoid

/ˌɔːθə(ʊ)ˈpɪnəkɔɪd/