General synonyms:
* Prejudiced: This is a very common synonym, often used interchangeably with "biased."
* Partisan: This implies a strong allegiance to a particular group or cause.
* Slanted: This refers to information that is presented in a way that favors a particular viewpoint.
* Unfair: This emphasizes the lack of impartiality and equity.
* Predisposed: This suggests a predisposition towards a particular opinion or outcome.
More specific synonyms:
* One-sided: This emphasizes the lack of balance in the presentation of information.
* Partial: This indicates a preference for one side over another.
* Prejudiced against/in favor of: This is a more specific way of indicating the direction of the bias.
* Dogmatic: This suggests a strong, inflexible belief that is not open to questioning.
* Bigoted: This refers to a strong, irrational prejudice, often based on race, religion, or other factors.
The best synonym for "biased" will depend on the specific context of your writing.