smear
Definitions
To coat, cover, or mark with a greasy, sticky, or dirty substance.
To damage or attempt to damage the reputation of someone by false or defamatory accusations.
A blurred or streaky mark made by or as if by a greasy or sticky substance.
Examples
The child managed to smear chocolate all over his clean white shirt.
The political candidate accused his opponent of running a smear campaign to damage his reputation.