Definition of mid-parent in English:

mid-parent

Pronunciation /ˈmɪdˌpɛːrənt/ /ˈmɪdˌpɛːr(ə)nt/

noun

Anthropology Genetics
  • Originally: a hypothetical parent of composite sex whose height is the average of the actual height of the father, and the height of the mother multiplied by the ratio of male to female height in the population. Later: a notional individual having the value of some property or trait equal to the average of the value of each parent.

Origin

Late 19th century; earliest use found in Francis Galton (1822–1911), biostatistician, human geneticist, and eugenicist. From mid + parent.