The crossword solution for the term 'Flame Output' is 'HEAT'. HEAT is a form of energy that is transferred from one object to another due to a difference in temperature. HEAT is produced by combustion, which is the process of burning fuel such as wood, coal, or gas. HEAT is also produced by friction, which is the rubbing together of two surfaces. HEAT is an important part of many industrial processes, such as welding and smelting.