(b) Any similar oxide of hydrocarbon radicals; as, amyl ether; valeric ether. {Complex ether}, {Mixed ether} (Chem.), an oxide of two different radicals in the same molecule; as, ethyl methyl ether, {C2H5.O.CH3}. {Compound ether} (Chem.), an ethereal salt or a salt of some hydrocarbon as the base; an ester. {Ether engine} (Mach.), a condensing engine like a steam engine, but operated by the vapor of ether instead of by steam.