The word "un-sure" refers to a state of uncertainty or doubt. Antonyms for the word "un-sure" include confident, certain, sure, convinced, definite, and assured. If you are confident about something, you believe in your ability to handle it effectively. Being certain involves having a conviction that something is true or accurate. When you are sure about something, you have no doubts or hesitations. Being convinced is similar to being sure, as it involves having a strong belief in a particular idea or concept. Definite refers to something that is precise, specific, and unambiguous. Finally, being assured involves having complete faith in your abilities or in a particular situation.