A type of hang over that catches the victim completely unaware. After a night of heavy drinking the victim will be lulled into a false sense of security when they awake in the morning with a clear head and a sunny disposition. The hangover will then ambush the victim some time in the late afternoon.
I drank far too much last night but I awoke bright as a button at 9am. I thought it would be a fantastic idea to do some DIY that I had been putting, however at around 2pm I was struck down by a merciless guerrilla hangover and spent the remainder of the day with my head in the toilet.