Ohno Second - n The brief fraction of time that it takes to realize you've made a huge mistake. Ohno seconds nearly always occur after you've hit the enter key or initiated some action that can be neither stopped or retracted.
Reminds me of the scene in Goodfellas where Pesci gets whacked. He walk into the room where he is going to get "made" and sees an empty room. At that moment he knows he is in for a bullet to the back of the head and his last words are "Oh No!".