What does it mean to "vacillate"?

To "vacillate" means to be undecided or to waver between different options or opinions. This term captures the essence of indecision, where an individual may fluctuate in their thoughts or choices rather than committing to a single course of action. It often implies a struggle to settle on a decision, leading the person to oscillate or swing back and forth without resolution.

In contrast, the other options suggest clarity or decisiveness. Quick decision-making, confidence in action, or diligent work imply a firm commitment to a particular stance or behavior, which is the opposite of what "vacillate" represents. Thus, being undecided aligns perfectly with the definition of vacillate.