Being undetermined means that something is not yet decided, fixed or settled. Therefore, its antonyms would be the opposite of that which include being certain, decisive, clear, resolved or settled. When we are certain, we have a clear idea or understanding of something and there is no doubt or uncertainty. Likewise, when we are decisive, we make firm decisions without hesitation. A situation is considered resolved when a final decision has been made, and a dispute or problem has been solved. Lastly, being settled means that something is agreed and arranged without any room for doubt, question or hesitation.