A flicker is a man that suffers from LDS (little dick syndrome) to such a severe degree that he must flick the last few drops of pee off his member because it is to short to shake.
A flicker is when a man is done pissing in the urinal he has to flick the last few droplets into the urinal, because his penis is to short to shake. This creates a problem, when he flicks the droplets it never makes it into the urinal, but falls to the floor creating the famous random pool of piss.
A person that automatically flicks on every light they pass while walking into the office, regardless of the proximity of his or her desk to the light in question.
"I prefer to work with the lights off because the ambient light is sufficient, but a flicker just walked by and turned all the lights on, despite the fact that his office is two floors up and these lights have no effect on him."