Definition

a duty formerly asserted by white people to manage the affairs of nonwhite people whom they believed to be less developed

This phrase comes from a poem (by the same name) by the imperialist poet Rudyard Kipling. It was about the Philippine American War, where Kipling encourages the American annexation and colonisation of Philippine Islands.

an advertisement of Pears Soap which talks about White Man’s burden and how teaching cleanliness will fulfill it.