/ ˈblækən; NAmE / verb
1.
to make sth black; to become black :
[ vn ]
Their faces were blackened with soot.
Smoke had blackened the walls.
[also v ] ➡ note at burn
2.
[ vn ] blacken sb's name / reputation / character to say unpleasant things that give people a bad opinion of sb :
He accused the newspaper of trying to blacken his name.