The word "一晃" is formed by combining the character "一" (yī), meaning "one" or "a single", with "晃" (huǎng), meaning "to shake" or "to flash". Together, they create an idiomatic compound where "一" emphasizes a singular, brief instance, and "晃" contributes the sense of a quick, fleeting motion, resulting in the meaning "in a flash" or "in the blink of an eye", used to describe time passing rapidly.