Having an acidic taste or smell, similar to that of vinegar or lemon. The milk had gone sour, so she had to throw it away.
Unpleasant or unfriendly in demeanor or attitude. His sour expression made it clear he was not happy with the decision.
Having a disagreeable or negative effect or outcome. The negotiations took a sour turn when neither party could agree on the terms.
Describing a musical tone or note that is noticeably out of tune, harsh, or dissonant. The trumpet hit a sour note during the solo.
Off-key or harsh in sound; not accurately pitched. The violinist hit a sour note during the solo.