So disgusting or disturbing that it makes you feel physically ill or deeply offended.
From the verb 'sicken' (to make sick) plus the suffix '-ing,' creating an adjective that describes what causes sickness or disgust. Related to 'sick' from Old English 'seoc.'
Your brain literally bridges the gap between 'sickening' in the physical sense and 'sickening' morally—both use the same disgust circuits, which is why we use stomach words for moral outrage!
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