spying

nouns

keeping a secret or furtive watch
spying
is derived from
spy
is a type of (narrower)
a purposeful surveillance to guard or observe
vigil, watch
the act of keeping a secret watch for intelligence purposes
spying, undercover work
is derived from
spy
the act of detecting something; catching sight of something
catching, detection, espial, spotting, spying
is derived from
spy