hol·o·caust 
(hŏlə-kôst′, hōlə-)
(hŏlə-kôst′, hōlə-)n.
1. Great destruction resulting in the extensive loss of life, especially by fire.
2.
a. Holocaust The genocide of European Jews and other groups by the Nazis during World War II: "Israel emerged from the Holocaust and is defined in relation to that catastrophe" (Emanuel Litvinoff).
b. A massive slaughter: "an important document in the so-far sketchy annals of the Cambodian holocaust" (Rod Nordland).
3. A sacrificial offering that is consumed entirely by flames.
[Middle English, burnt offering, from Old French holocauste, from Latin holocaustum, from Greek holokauston, from neuter of holokaustos, burnt whole : holo-, holo- + kaustos, burnt (from kaiein, to burn).]
hol′o·caustal, hol′o·caustic adj.
Usage Note: Holocaust has a secure place in the language when it refers to the massive destruction of humans by other humans. In our 1987 survey 99 percent of the Usage Panel accepted the use of holocaust in the phrase nuclear holocaust. Sixty percent accepted the sentence As many as two million people may have died in the holocaust that followed the Khmer Rouge takeover in Cambodia. But because of its associations with genocide, people may object to extended applications of holocaust. The percentage of the Panel's acceptance drops sharply when people use the word to refer to death brought about by natural causes. In our 1999 survey 47 percent approved the sentence In East Africa five years of drought have brought about a holocaust in which millions have died. Just 16 percent approved The press gives little coverage to the holocaust of malaria that goes on, year after year, in tropical countries, where there is no mention of widespread mortality. The Panel has little enthusiasm for more figurative usages of holocaust. In 1999, only 7 percent accepted Numerous small investors lost their stakes in the holocaust that followed the precipitous drop in stocks. This suggests that these extended uses of the word may be viewed as overblown or in poor taste.
Word History: Totality of destruction has been central to the meaning of holocaust since it first appeared in Middle English in the 1300s, used in reference to the biblical sacrifice in which a male animal was wholly burnt on the altar in worship of God. Holocaust comes from Greek holokauston, "that which is completely burnt," which was a translation of Hebrew 'ōlâ (literally "that which goes up," that is, in smoke). In this sense of "burnt sacrifice," holocaust is still used in some versions of the Bible. In the 1600s, the meaning of holocaust broadened to "something totally consumed by fire," and the word eventually was applied to fires of extreme destructiveness. In the 1900s, holocaust took on a variety of figurative meanings, summarizing the effects of war, rioting, storms, epidemic diseases, and even economic failures. Most of these usages arose after World War II, but it is unclear whether they permitted or resulted from the use of holocaust in reference to the mass murder of European Jews and others by the Nazis. This application of the word occurred as early as 1942, but the phrase the Holocaust did not become established until the late 1950s. Here it parallels and may have been influenced by another Hebrew word, šô'â, "catastrophe" (in English, Shoah). In the Bible šô'â has a range of meanings including "personal ruin or devastation" and "a wasteland or desert." Šô'â was first used to refer to the Nazi slaughter of Jews in 1939, but the phrase haš-šô'â, "the catastrophe," became established only after World War II. Holocaust has also been used to translate ḥurbān, "destruction," another Hebrew word used as a name for the genocide of Jews by the Nazis.