Whakapohane is the Māori practice of baring one's buttocks with the intent to offend. It is as offensive in Māori as in Pākehā

Pakeha

Pākehā is a Māori language word for New Zealanders who are "of European descent". They are mostly descended from British and to a lesser extent Irish settlers of the nineteenth and twentieth centuries, although some Pākehā have Dutch, Scandinavian, German, Yugoslav or other ancestry...

 culture — symbolises the birthing act, and renders the recipient noa ("base").

A famous recent example of whakapohane being performed was by Dun Mihaka

Dun Mihaka

Te Ringa Mangu Nathan Mihaka or Dun Mihaka is a Māori activist, author, and political candidate in New Zealand.Mihaka has been involved in a number of campaigns regarding Māori rights, and was involved in the Bastion Point land dispute...

 to Diana, Princess of Wales

Diana, Princess of Wales

Diana, Princess of Wales was the first wife of Charles, Prince of Wales, whom she married on 29 July 1981, and an international charity and fundraising figure, as well as a preeminent celebrity of the late 20th century...

 and Prince Charles during the 1983 royal tour of New Zealand.