Boiler/ˈbɔɪlər/ Definition 1 of 3Pro Tip 1/3Heat Source Remember that a boiler's primary function is to heat a space or liquid. Our new boiler can quickly heat the entire pool. Pro Tip 2/3Home Context Boilers are often found in homes, making it a familiar household term. We had to call a technician to fix our home boiler. Pro Tip 3/3Energy Types Boilers can be powered by gas, electricity or other fuels. Switching to an electric boiler can reduce carbon emissions.