1. Of or relating to an autotroph, an organism capable of making nutritive organic molecules from inorganic sources via photosynthesis (involving light energy) or chemosynthesis (involving chemical energy).
2. Self-sustaining or self-nourishing organisms (e.g. green plants, algae, and certain bacteria) that have the ability to synthesize their own food from inorganic materials, e.g. carbon dioxide and nitrogen.