- any material, as coal, oil, gas, wood, etc., burned to supply heat or power
- fissile material from which nuclear energy can be obtained, as in a nuclear reactor
- anything that maintains or intensifies strong feeling, etc.
Origin of fuelMiddle English fewell from Old French fouaille from Medieval Latin fuale, focale from foca, hearth, for Classical Latin focus, fireplace: see focus
transitive verbfu′eled or fu′elled, fu′el·ing or fu′el·ling