Consciousness is being aware of -- and capable of interacting with -- your surroundings. Consciousness is not an all or nothing state. Healthcare providers look at levels of consciousness, usually assessing a patient's ability to follow instructions, communicate verbally, and track objects with his eyes.
In medical terms, getting knocked out is a loss of consciousness. At the worst, a patient is referred to as being unresponsive, which means she doesn't respond to any type of stimulus, including yelling, shaking or pain.