Despicable means extremely unpleasant or objectionable. Someone who does something truly awful might be considered despicable.
We often use "despicable" to describe someone's actions or behavior that are shocking and unacceptable. Imagine a politician making huge amounts of money while their citizens struggle to make ends meet - that could be seen as very despicable. We also sometimes use it for characters in movies who are just plain mean-spirited, like the villain in a cartoon. In general, when someone does something so bad or selfish that you want to call them out on it, "despicable" is a good word to use.
Fit or deserving to be despised; contemptible; mean.
