Boundless energy is a term used to describe an inexhaustible source of energy that can be used for a variety of purposes. The two crossword solutions for this term are PEP (3 letters) and SOLARPOWE (9 letters). PEP stands for Positive Energy Power, which is a form of renewable energy that is generated from natural sources such as the sun, wind, and water. SOLARPOWE stands for Solar Power, which is a form of renewable energy that is generated from the sun's rays. Both of these forms of energy are considered to be boundless, meaning they are virtually inexhaustible and can be used for a variety of purposes.