Self-opinionated is a term used to describe someone who is very sure of their own opinions and often believes they are always right. If you want to describe this kind of person without using the word "self-opinionated," there are a few synonyms you can use. You might call them arrogant, egotistical, or conceited. Other options include haughty, pompous, or opinionated. Some might describe this kind of person as stubborn or bull-headed, while others might use the phrase "know-it-all." No matter how you describe them, someone who is self-opinionated can be difficult to deal with and may not be open to hearing other perspectives.