Definition of langue d'oïl in English:

langue d'oïl

noun

  • [mass noun] The form of medieval French spoken north of the Loire, generally characterized by the use of oïl to mean ‘yes’, and forming the basis of modern French.

Origin

From Old French langue language (from Latin lingua tongue), d' (from de of), and oïl (from Latin hoc ille) yes. Compare with langue d'oc.

Pronunciation:

langue d'oïl

/lɒ̃(ɡ) ˈdɔɪl/