The phrase "blew top" is typically used to describe a person who loses their temper or becomes very angry. Some antonyms for this phrase may include "steady," "controlled," or "calm." When a person is able to maintain their composure and avoid becoming excessively upset or agitated, they are exhibiting a sense of control and calmness. Other antonyms that may apply to the phrase "blew top" include "unfazed," "collected," and "placid." These words all describe someone who is able to remain cool-headed and emotionally stable in the face of stress, frustration, or anger.