an oil used for fuel, especially one used as a substitute for coal, as crude petroleum.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
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Historical Examples of fuel oil
a liquid petroleum product having a flash point above 37.8°C: used as a substitute for coal in industrial furnaces, domestic heaters, ships, and locomotives
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012