A more thorough explanation:

taint, n.

1. A conviction of a serious crime.
2. A person who has been convicted of a serious crime. See ATTAINDER.

taint, vb.

1. To make something bad or harmful by adding a harmful quality or principle.
2. To contaminate or corrupt something.
3. To slightly affect something in a negative way.

Examples:

• After his conviction for embezzlement, he carried the taint of a criminal for the rest of his life.
• The company's reputation was tainted by the scandal.
• The food was tainted with bacteria, causing many people to become sick.
• The politician's association with a known criminal tainted his campaign.

These examples illustrate how the term "taint" can refer to a conviction of a serious crime, a person who has been convicted of a serious crime, or the contamination or corruption of something. In the first example, the person's conviction taints his reputation. In the second example, the scandal taints the company's reputation. In the third example, the bacteria taints the food. In the fourth example, the politician's association with a criminal taints his campaign.