The act of driving slowly in front of someone, often preceded by cutting them up at a junction.
The nose-gater ususally drives at around 24.5 in a 30 zone. This can be due to a number of reasons:excessively new car (worried that air friction may scratch paintwork); old age (can't see, reaction speed gone); kids in car (irrational spawn-protecting behaviour); Micra driver (inexplicable) etc..
The opposite of tail-gating. Especially prevalent when you are trying to get somewhere in a hurry.