The dictionary says that cierto means true or certain.
In English, saying something is certain is very different from saying it’s true. If I say “it is not certain that it will rain tomorrow”, that’s different from “it is not true that it will rain tomorrow”. Certain means almost like necessarily true or logically true based on evidence, whereas true is kind of circumstantial.
What is interesting, is that in DeepL, the meaning of cierto changes depending on whether the subjunctive is used:
“No es cierto que vaya a llover mañana. “ means “It is not certain that it will rain tomorrow. “
“No es cierto que va a llover mañana. “ means “It is not true that it will rain tomorrow. “
Is this just a case of using cierto in a subjunctive clause, or subjunctive like context, or is the meaning of cierto just different or ambiguous by default?