The term is often used without a definition. Some authors define the term "high-energy" to be equivalent to "chemically unstable", while others reserve the term for high-energy phosphates, such as the Great Soviet Encyclopedia which defines the term "high-energy compounds" to refer exclusively to those.
The IUPAC glossary of terms used in ecotoxicology defines a primary producer as an "organism capable of using the energy derived from light or a chemical substance in order to manufacture energy-rich organic compounds". However, IUPAC does not formally define the meaning of "energy-rich".