The Oxford English Dictionary states:
Definition of horror
noun
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1 [mass noun] an intense feeling of fear, shock, or disgust:children screamed in horror
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a thing causing a feeling of horror:photographs showed the horror of the tragedy[count noun]:the horrors of civil war
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a literary or film genre concerned with arousing feelings of horror:[as modifier]:a horror film
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intense dismay:to her horror she found that a thief had stolen the machine
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[as exclamation] (horrors) chiefly humorous used to express dismay:horrors, two buttons were missing!
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[in singular] intense dislike:many have a horror of consulting a dictionary
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(the horrors) an attack of extreme nervousness or anxiety:the mere thought of it gives me the horrors
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2 informal a bad or mischievous person, especially a child:that little horror Zach was around
Middle English: via Old French from Latin horror, from horrere ‘tremble, shudder’ (see horrid)
Shannon Cotton 