ENGLISH
REFERENCE

spy

n. · v.
US //ˈspaɪ// UK //spˈaɪ// spy
  1. 1 secret agent (n.)
    B1 Intermediate

    a person who secretly collects information about an enemy, a government, or a business.

    an individual employed by a government or organisation to collect secret information regarding a competitor or enemy.

    Example

    The spy was caught trying to steal secret documents from the embassy.

    Example

    Intelligence agencies often spend years cultivating a single spy within a foreign government to ensure a steady flow of high-level information.

  2. 2 to watch secretly (v.)
    B1 Intermediate

    to watch someone or something secretly to find out information.

    to observe a person, group, or country secretly and continuously. Often takes the preposition 'on'.

    Example

    The children liked to spy on their older brother from the treehouse.

    Example

    The corporation was accused of hiring private investigators to spy on its competitors' research and development facilities.

    Usage

    Commonly used with the preposition 'on' followed by the target.

Show 2 more sensesShow fewer
  1. 3 to catch sight of (v.)
    C1 Advanced Literary

    to suddenly see or notice something, especially something far away or hidden.

    to catch sight of or detect something through careful observation. Transitive in this sense.

    Example

    From the top of the hill, she managed to spy a small cottage in the valley.

    Example

    After hours of scanning the horizon with his binoculars, the lookout finally spied a thin plume of smoke rising from the distant island.

  2. 4 football defender (n.)
    C2 Proficiency American English Technical Sport

    a player in American football whose job is to watch and follow a specific opponent.

    a defensive player assigned to mirror the movements of a specific offensive player, typically the quarterback, to prevent a run.

    Example

    The coach decided to use a linebacker as a spy to stop the quarterback from running.

    Example

    By employing a fast linebacker as a spy, the defense successfully neutralised the quarterback's ability to scramble for first downs.

    Usage

    Used as a countable noun in a sports strategy context.

Origin

From Middle English spien, aphetic variant of earlier espien (“to espy”), from Old French espier (“to spy”), from Frankish spehōn (“to spy”), from Proto-Germanic spehōną (“to see, look”), from Proto-Indo-European *speḱ- (“to look”). Akin to German spähen (“to spy”), Dutch spieden (“to spy”). The noun displaced native Old English sċēawere (literally “watcher”), which was also the word for "mirror." In this sense, the verb displaced Old English sċēawian, which was also the word for "to watch" and became the Modern English word show. Distant cognate vie PIE with Latin speculātor, Ancient Greek κατάσκοπος (katáskopos). Compare typologically Russian согляда́тай (sogljadátaj) (akin to гляде́ть (gljadétʹ)).

© 2026 English Reference