(noun) A moment of sudden realization, inspiration, insight, recognition or comprehension

Usage: Oprah Winfrey had a major aha moment on her talk show in 1990 while discussing forgiveness and letting go of the past. "That was a transcendent moment for me – bigger even than an aha," she recalled in 2011. (Though the catchphrase has long been associated with Winfrey, it actually originated in 1939, according to Webster.)