It is the feeling which a persons gets directly before understanding, and not understanding. This is linked with the feeling of "deja vu" which is proven to be broken memories brought back through old thought patterns. An individual will know at the point of experience of "SNOPA" exactly what the feeling is.
Bob 1"Jesus christ, that SNOPA hit me like a bullet"
Bob 2"First time eh?"
Bob 1 "Tja!"