Fuel \Fu"el\, n. [OF. fouail, fuail, or fouaille, fuaille, LL. focalium, focale, fr. L. focus hearth, fireplace, in LL., fire. See {Focus}.] [Formerly written also {fewel.}] 1. Any matter used to produce heat by burning; that which feeds fire; combustible matter used for fires, as wood, coal, peat, etc. [1913 Webster] 2. Anything that serves to feed or increase passion or excitement. [1913 Webster] {Artificial fuel}, fuel consisting of small particles, as coal dust, sawdust, etc., consolidated into lumps or blocks. [1913 Webster]