1. To be expose something to or contaminate something with some substance or agent that is infectious, toxic, or otherwise dangerous or unpleasant. Officials have confirmed that the water supply has been tainted by lead. They have been forced to recall nearly 3 million tons of canned tomatoes that may have been tainted by botulin.

2. To be spoiled, ruined, or degraded by the presence or introduction of something terrible, tragic, or deeply unpleasant. Their victory has been tainted by the many lives lost in the battle. It's a shame seeing such an incredible career being tainted by this scandalous behavior.