Learn how to say Plateaux correctly in English with this tutorial pronunciation video.
Oxford dictionary definition of the word plateau:
noun (plural plateaux /-təʊz/ or plateaus)
1an area of fairly level high ground.
[as modifier] denoting a group of American Indian peoples of the high plains of western Canada and the US, including the Nez Percé.
2a state of little or no change following a period of activity or progress:
the peace process had reached a plateau
verb (plateaus, plateauing, plateaued)
reach a state of little or no change after a period of activity or progress:
the industry’s problems have plateaued out
late 18th century: from French, from Old French platel, diminutive of plat ‘level’
The plural of the noun can be spelled either plateaux (as in the original French) or plateaus.