1. A description of those parts of the ocean that are not reached by sunlight, or plants that grow there without photosynthesizing: "The remote controlled camera was able to explore the aphotic depths of the ocean, looking for rare life forms."
2. A reference to any environment or habitat that has no sunlight of any biological significant intensity: "The fish that have lived for a long time in the dark cave evolved into a state of blindness because of their aphotic environment."
3. Etymology: literally, "no light".