I know the word "watch" is used as a synonym of spy. Are there other synonyms that are used by native speakers?


Maybe the word "snoop" could be a good synonym.

I caught him snooping around in my office.

Reporters were snooping on the celebrities


You can also use "notice", "observe", "monitor", "track", "keep an eye on", "keep track of", "keep tabs on" -- all these have slightly different meanings, depending on what you mean to convey when you'd use spy.

  • Use notice if you mean to say that you suddenly noticed a detail of some sort.
  • Use observe if you mean to say that you're dispassionately watching something unfold, or noticing a detail or series of details with emotional detachment.
  • Use monitor if you mean to say that you're continually watching something with some measurement in mind that would prompt you to step in or take action if the measurement goes outside a certain range.
  • All of the keep... phrases are informal ways of saying that you're going to spend some casual effort going forward to (essentially) monitor something -- they're mostly casual ways of using the monitor sense of spy.

Notice that, strictly speaking, spy can carry a connotation of secret, covert behaviour. When you spy you have an agenda of some sort, or a secret purpose. The most neutral version of spy is to suddenly notice something: the longer the activity spent observing, the more you convey a sense of secretness.


To spy, in the sense of watching someone or something, could also mean keeping that thing under surveillance.

In that sense, spy (the verb) has approximately the same meaning as surveil.

  • 1
    Is that formal? Can I use it informally?
    – Ehsan
    Feb 10 '11 at 14:34
  • Surveil is not formal, but it's not commonly used, either. Feb 10 '11 at 14:49
  • Not formal? Meaning what exactly?
    – Ed Guiness
    Feb 10 '11 at 14:51
  • Surveillance and reconnoiter are both specialised terms associated with government/military action; case (as in "I cased the joint" -now quite archaic) equally implies some formal, quasi-legitimate undertaking. You can use them all informally, but you should know they have those associations.
    – fortunate1
    Feb 10 '11 at 14:53

If you mean to spy then you can use snoop (informal), keep under surveillance/observation, keep a watch on, keep an eye on, observe, spot.
If you mean spy used as noun, then you can use secret agent, undercover agent, intelligence agent, double agent, mole, snoop.

Which word/phrase suits better depends on the context.

  • "intelligence agent", not "intelligent agent". Not bad enough to warrant a -1, though. Feb 10 '11 at 21:57
  • Whoops… It seems I made it rhyme with agent.
    – apaderno
    Feb 10 '11 at 22:02

infiltrator, undercover agent


This depends on context and connotation.
There are spies-heroes and there are sneaks, sneakers, snitches, informers, finks, noses, squeakeres, denunciators, questmans, talebearers, whistlers, grass, nark, noser, stool pigeon, checker, squeal, zuch, rat, rounder, delator, etc.

Seems like negative characters are always have better and more specific characteristic terms than positive ones.

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