Invar invalued • invariability · · · Info · Definitions · Characters · · Invar · · Text Latin · · Script 5 · · Length Definitions · · · (noun) an alloy of iron and nickel having a low coefficient of thermal expansion; used in tuning forks and measuring tapes and other instruments. · · Noun Definition 1 Characters · · I latin capital letter i U+0049 a latin small letter a U+0061 n latin small letter n U+006E r latin small letter r U+0072 v latin small letter v U+0076