spiegeleisenPronunciation: /ˈspiːg(ə)lˌʌɪz(ə)n/Definition of spiegeleisen noun [mass noun] an alloy of iron and manganese, used in steel-making. Origin: mid 19th century: from German, from Spiegel 'mirror' + Eisen 'iron'spiegeleisen in other Oxford dictionaries Definition of spiegeleisen in the US English dictionary