The first word said when stepping on the bedside lamp plug which you forgot to plug in to the wall socket.
The word is usually followed by 'Bastard' or 'Cunt' or both, but others can be thrown into the mix to reduce the pain. And usually shouted for approx 15 minutesrepeatedly whilst standing on one leg.
'Turns out light to get into bed and bedside lamp plug is laying on floor'