Definition of proto-diasystem in US English:

proto-diasystem

noun

Linguistics
rare
  • A hypothetical reconstruction of the system of linguistic relationships in a proto-language.

Origin

1960s; earliest use found in Word (International Linguistic Association). From proto- + diasystem.

Pronunciation

proto-diasystem

/ˌprəʊtə(ʊ)ˈdʌɪəsɪstɪm/