Definition of retrocede in US English:

retrocede

verb

[with object]rare
  • Cede (territory) back again.

    ‘Spain retroceded the colony to France’
    • ‘There is even a precedent: The Virginia portion of D.C. was retroceded in 1846, no muss, no fuss, and became Arlington County.’
    • ‘Spain retroceded the colony to France just prior to Napoleon's sale of the Louisiana territory to the United States in 1803.’
    • ‘It's possible that Congress could retrocede all or most of the District to Maryland, just as it retroceded the Virginia part of the District (which originally included a chunk of Virginia) in the 1840s to Virginia.’
    • ‘At midnight, 30 June 1997, Hong Kong was retroceded to PRC sovereignty, an event witnessed by millions around the world via a televised Sino-British ceremony in Hong Kong.’
    • ‘The French emperor retroceded Venetia to Italy, fulfilling the promise he had made in 1859 to ‘unify Italy from the Alps to the Adriatic’.’

Origin

Mid 17th century in sense ‘retreat, recede’: from French rétrocéder ‘go back’.

Pronunciation

retrocede

/ˌretrəˈsēd//ˌrɛtrəˈsid/