Definition of pia-arachnoid in US English:

pia-arachnoid

(also piarachnoid)

noun

Anatomy
  • The pia mater and the arachnoid (considered as a structural or functional unit with two layers).

Origin

Late 19th century; earliest use found in The Lancet. From pia + arachnoid.

Pronunciation

pia-arachnoid

/ˌpʌɪə(r)əˈraknɔɪd/