Killer Whales are highly intelligent animals with highly complex social structures, and live in a matriarchal society. They posses the ability to communicate to each other with clicks, whistles, and pulsed calls. Different Killer Whale clans have different "dialects," or different ways of speaking. Their language shows intelligence, which they owe to their neocortex in their brain. The neocortex deals with higher level thinking and abilities like spatial reasoning, which is just like imagining a house and the distance it is from the next house; conscious thought; and language.
Killer whales possess notochord, which is no more than a cartilaginous skeletal rod supporting the body, according to webster's dictionary.
http://onlinelibrary.wiley.com/doi/10.1002/ar.a.20075/full This is a link to an interesting research paper on the brain of a killer whale. While a little of the scientific jargon flew over my head, I was able to get the gist of the article: killer whale brains are similar to bottle-nose and the common dolphin's brain. However, their brains are more intricate, and convoluted (which means folded and is equated with higher processing power) in the cerebral hemisphere, which is the half of the brain dealing with speech, thought, emotions, and muscle functions. Killer Whales, however, have a smaller corpus callosum, which is a flat bundle of neurofibers in the brain, which the researchers believe may have negative effects because one the corpus callosum's main functions is communication between brain hemispheres.
This high brain capacity for an animal of such great physical prowess leads to a deadly and efficient predator. The orcas concoct some excellent hunting strategies that seem like humans made them up. For example, in the video below killer whales work together to wash a seal off an ice chunk.