Something disgusting is awful in a way that makes you want to throw up — it's really, really yucky. Nobody likes disgusting things.
Stepping in dog poo is disgusting — in other words, revolting and gross. Some people think spiders are disgusting; others find meatloaf disgusting; it just depends on what your tastes and tolerances are. If a politician is caught taking bribes, people say "That behavior is disgusting!" If your favorite team loses 20 games in a row, that might seem disgusting. Pretty much anything horrible, terrible, or nasty can be called disgusting.
