1. A hard piece of snot, just inside the nostril but visible to anyone within conversation range. Usually hangs from and surrounds a nose hair the way wax surrounds a candle wick.
2. A semi-hard piece of snot that flies out of you nostril into a handkerchief or the palm of your hand when you sneeze.
When he sneezed, a snedley shot out his nose and landed in my french fries.
An urban derivative of sneaky, but more commonly used when secret missions are on the plan.
Also associated is the snealy look, a look of supreme sneakiness with undertones of smugness and arousal. This has been adopted in favour over a handshake.