The phrase "gat under way" is an idiom that means to start or begin something. Antonyms for this phrase could include "stop," "halt," "cease," "discontinue," "end," or "finish." These words suggest a complete opposite action or intent to the idea of getting something underway. Other antonyms might include "delay," "postpone," or "procrastinate," which indicate a lack of urgency or intention to begin something. It is important to choose the right antonym for the context of the situation, as they can convey very different meanings and implications.