Learn how to say Holocausts correctly in English with this tutorial pronunciation video.
Oxford dictionary definition of the word holocaust:
1destruction or slaughter on a mass scale, especially caused by fire or nuclear war:
a nuclear holocaust
(the Holocaust) the mass murder of Jews under the German Nazi regime during the period 1941-5. More than 6 million European Jews, as well as members of other persecuted groups, were murdered at concentration camps such as Auschwitz.
2 historical a Jewish sacrificial offering which was burnt completely on an altar.
Middle English: from Old French holocauste, via late Latin from Greek holokauston, from holos ‘whole’ + kaustos ‘burnt’ (from kaiein ‘burn’)