When you stare at someone, or someone stares or spies on you
repeatedly, either
checking you out or in a disapproving way.
It can be used to describe the culprit and also what they are doing.
katy: I think we're being cocknosed.
Anna:
Yeah i know, it's that cocknose
over there, could he be any more cocknosey!
Katy: I know, cocknosers really
get my goat.