The word "unbelievable" means not able to be believed or too extraordinary to be true. Some antonyms for "unbelievable" are:
Believable: This is the most straightforward opposite. When something is believable, it is capable of being accepted as true or plausible. For example, "The witness gave a believable account of the events, in contrast to the previous unbelievable story." Believable implies a sense of credibility and trustworthiness.
Plausible: Something that is plausible also seems likely or reasonable to be true. For instance, "The theory put forward was plausible and made more sense than the unbelievable speculation." Plausible suggests that there are good reasons to think it could be true.
Credible: This word emphasizes being worthy of belief or trust. For example, "The source was credible, so the information was not unbelievable as before." Credible indicates that there is a solid basis for believing what is being said or presented.
In conclusion, these antonyms of "unbelievable" offer alternatives that convey a sense of trust, likelihood, and acceptability. While unbelievable implies doubt and astonishment, believable, plausible, and credible suggest that there is a rational basis for accepting something as true.