from The American Heritage® Dictionary of the English Language, 5th Edition.

  • noun One who secretly collects information concerning the enemies of a government or group.
  • noun One who secretly collects information for a business about one or more of its competitors.
  • noun One who secretly keeps watch on another or others.
  • intransitive verb To watch or observe secretly.
  • intransitive verb To discover by close observation.
  • intransitive verb To catch sight of; see.
  • intransitive verb To engage in espionage.
  • intransitive verb To investigate or observe something, especially in secret.

from The Century Dictionary.

  • To discover at a distance, or from a position of concealment; gain sight of; see; espy.
  • To discover by close search or examination; gain a knowledge of by artifice.
  • To explore; view, inspect, or examine secretly, as a country: usually with out.
  • To ask; inquire; question.
  • To search narrowly; scrutinize; pry.
  • To play the spy; exercise surveillance.
  • noun A person who keeps a constant watch on the actions, motions, conduct, etc., of others; one who secretly watches what is going on.
  • noun A secret emissary who goes into an enemy's camp or territory to inspect his works, ascertain his strength and his intentions, watch his movements, and report thereon to the proper officer. By the laws of war among all civilized nations a spy is liable to capital punishment.
  • noun The pilot of a vessel.
  • noun Au advanced guard; a forerunner.
  • noun [In the following passage, spy is supposed by some to mean that which precedes and announces the time for the assassination of Banquo, by others the very eye, the exact moment.
  • noun A glance; look; peep.
  • noun An eye.
  • noun Synonyms Emissary, Spy (see emissary), scout.

from the GNU version of the Collaborative International Dictionary of English.

  • intransitive verb To search narrowly; to scrutinize.
  • noun One who keeps a constant watch of the conduct of others.
  • noun (Mil.) A person sent secretly into an enemy's camp, territory, or fortifications, to inspect his works, ascertain his strength, movements, or designs, and to communicate such intelligence to the proper officer.
  • noun money paid to a spy; the reward for private or secret intelligence regarding the enemy.
  • noun (Eccl.) the Wednesday immediately preceding the festival of Easter; -- so called in allusion to the betrayal of Christ by Judas Iscariot.
  • transitive verb To gain sight of; to discover at a distance, or in a state of concealment; to espy; to see.
  • transitive verb To discover by close search or examination.
  • transitive verb To explore; to view, inspect, and examine secretly, as a country; -- usually with out.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

  • noun A person who secretly watches and examines the actions of other individuals or organizations and gathers information on them (usually to gain an advantage).
  • verb intransitive To act as a spy.
  • verb transitive To spot at a distance.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • verb secretly collect sensitive or classified information; engage in espionage
  • noun a secret watcher; someone who secretly watches other people
  • verb catch sight of
  • verb catch sight of; to perceive with the eyes
  • verb watch, observe, or inquire secretly
  • noun (military) a secret agent hired by a state to obtain information about its enemies or by a business to obtain industrial secrets from competitors


from The American Heritage® Dictionary of the English Language, 4th Edition

[Middle English spie, from Old French espie, from espier, to watch, of Germanic origin; see spek- in Indo-European roots.]

from Wiktionary, Creative Commons Attribution/Share-Alike License

Middle English spien, aphetic variant of earlier espien "to espy", from Old French espier ("to spy") (espie "a spy"), from Frankish *spehōn ("to spy"), from Proto-Germanic *spehōnan (“to see, look”), from Proto-Indo-European *spek- (“to look”). Akin to Old High German spehōn, spehhōn "to scout, look out for, spy" (German spähen "to spy"), Middle Dutch spien "to spy", Dutch bespieden "to spy on"


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