If you're disgusted, you're fed up, appalled, or sickened by something. You might, for example, be disgusted by the smell of your younger brother's dirty feet.
If you've had enough of listening to your wealthy cousin complain about all the international traveling she has to do, you're disgusted. And if the thought of eating the casserole your mom cooked is making you feel queasy, you're also disgusted. You can give someone a disgusted look — or just think disgusted thoughts — if they tell an offensive joke. Disgusted comes from the Middle French desgouster, "have a distaste for."