When someone is astounded by an inconspicuously profound statement, fact, or idea. When you blow someone's mind. See also: auto-epiphellatio.
My friend had an epiphellatio when I told him toothpaste can be used to remove stains from headlights, carpets, and leather.
My roommate wanted to know a way to easily make a grilled cheese sandwich. When I told him he could just turn the toaster sideways, he had an epiphellatio.
I performed auto-epiphellatio when I figured out I could make grilled cheese by turning the toaster sideways.
When I came up with the word epiphellatio today, I had an auto-epiphellatio.