Being taken aback is a phrase that describes feeling surprised, shocked, or stunned by something unexpected. The antonyms for this phrase would be descriptive words that convey a sense of preparedness, composure, and lack of surprise. Some of these words include unfazed, unperturbed, unsurprised, poised, unflappable, confident, and composed. These antonyms imply a sense of control over one's emotions and reactions, as well as a readiness to face any situation. When one is not taken aback, they show a level of maturity and an ability to handle unexpected events calmly and efficiently.