You have the definition right on. This can happen even without your knowledge. For more than five years I have had chronic lung infections, the most recent one landing me in the hospital with full blown pneumonia. Turns out that without my knowing it, when I drink or eat anything very liquid, my throat does not close off completely and I aspirate some of this into my left lung. There is nothing they can do to stop this, as the physical structures in the back of my mouth are now significantly different from the radiation and surgeries. Dysphagia can be subtle as in my case, or overt as in actually aspirating solids as well with dangerous consequences.