Dorsal is a word taken from anatomy (the study of the body) and refers to things that have to do with one's back. The movie "Jaws" should have been called "Dorsal Fin," because that's almost all you ever see of the famous shark.
Like dolphins and sharks, killer whales have prominent dorsal fins on their backs, but it's the ones on their tails you'll want to watch out for. You may have wondered why dogs, cats, and other animals carry their young around by the scruff of their necks. Well, the little one's dorsal sides have extra fat and fur to grab onto. The dorsal side is much harder to damage than the underside (the ventral side) where you'll find their tender tummies and tasty organs.