This phrase literally translates to 'a known evil is better than an unknown good.' It is used to express the idea that it's better to stick with a situation or person you are familiar with (even if it's bad), than to risk going for an unknown (even if it could turn out good).
Examples
- Spanish: No quiero cambiar de trabajo. Ya sé que este no es perfecto, pero es mejor malo conocido que bueno por conocer.
- English: I don't want to change jobs. I know this one isn't perfect, but a known evil is better than an unknown good.