Sickening describes something so disgusting, disturbing, or wrong that it makes you feel almost physically ill. When you see a bully picking on a younger child, you might call it sickening because it troubles you deeply. A particularly gruesome scene in a movie might be sickening to watch. The smell of rotten food is sickening. A corrupt politician stealing money meant for schools might commit sickening acts of greed.

The word captures that stomach-turning feeling you get when something is truly awful. It's stronger than just “bad” or “unpleasant.” Something sickening affects you viscerally, making you want to look away or step back. You might feel sickened by cruelty, by terrible injustice, or by something physically revolting.

Interestingly, people sometimes use sickening in a playful, exaggerated way about things that aren't actually disgusting but are impressively good. A talented gymnast might stick a perfect landing, and her teammate might joke, “That was sickening!” meaning it was so incredibly good it's almost unfair. But this casual usage is quite different from the word's primary meaning: something genuinely revolting or morally wrong.