formazan
noun
form·a·zan
| \ ˈfȯr-mə-ˌzan
\
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Medical Definition of formazan
: a hypothetical hydrazone CH4N4 related to formic acid and known only in the form of intensely colored derivatives of which some are obtained from colorless compounds by the reducing action of living tissues and serve as indicators of viability by color production
also
: any of these derivatives