Synonyms for Spying:

n.

following, interference, intrusion, voyeurism, wiretapping, prying. spying (noun)
detection, espial, catching, undercover work, spotting.
surveillance (noun)
espial, wiretapping, voyeurism, following.
watching (noun)
prying, observing.

v.

seeing (verb)
looking, sighting, Gazing, seeing, Inspecting, viewing, observing, regarding, Glancing, Glimpsing, Peering, discerning, watching, peeking, beholding, Perceiving, Witnessing, staring, glaring.

Other synonyms:

Other relevant words:
detection, undercover work, catching, spotting, following, prying, wiretapping, espial.

Usage examples for spying

  1. The idea, spying on you!" – Police Your Planet by Lester del Rey
  2. How much do they pay you a week to be all the time spying after your sister? – Carnival by Compton Mackenzie
  3. And true it is that I went about spying and listening everywhere for anything I could learn of Fru Falkenberg; and then at times, ay, many a night, I would call myself to account for that same thing, and torture myself with self- contempt. – Wanderers by Knut Hamsun