spy

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. An agent employed by a state to obtain secret information, especially of a military nature, concerning its potential or actual enemies.
2. n. One employed by a company to obtain confidential information about its competitors.
3. n. One who secretly keeps watch on another or others.
4. n. An act of spying.
5. v. To observe secretly with hostile intent.
6. v. To discover by close observation.
7. v. To catch sight of: spied the ship on the horizon.
8. v. To investigate intensively.
9. v. To engage in espionage.
10. v. To seek or observe something secretly and closely.
11. v. To make a careful investigation: spying into other people's activities.

Century Dictionary and Cyclopedia

1. To discover at a distance, or from a position of concealment; gain sight of; see; espy.
2. To discover by close search or examination; gain a knowledge of by artifice.
3. To explore; view, inspect, or examine secretly, as a country: usually with out.
4. To ask; inquire; question.
5. To search narrowly; scrutinize; pry.
6. To play the spy; exercise surveillance.
7. n. A person who keeps a constant watch on the actions, motions, conduct, etc., of others; one who secretly watches what is going on.
8. n. 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.
9. n. The pilot of a vessel.
10. n. Au advanced guard; a forerunner.
11. n. [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.
12. n. A glance; look; peep.
13. n. An eye.
14. n. Synonyms Emissary, Spy (see emissary), scout.

Wiktionary

1. n. A person who secretly watches and examines the actions of other individuals or organizations and gathers information on them (usually to gain an advantage)
2. v. To act as a spy.
3. v. To spot at a distance.

GNU Webster's 1913

1. v. To gain sight of; to discover at a distance, or in a state of concealment; to espy; to see.
2. v. To discover by close search or examination.
3. v. To explore; to view, inspect, and examine secretly, as a country; -- usually with out.
4. v. To search narrowly; to scrutinize.
5. n. One who keeps a constant watch of the conduct of others.
6. n. 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.

WordNet 3.0

1. v. secretly collect sensitive or classified information; engage in espionage
2. n. a secret watcher; someone who secretly watches other people
3. v. catch sight of
4. v. catch sight of; to perceive with the eyes
5. v. watch, observe, or inquire secretly
6. n. (military) a secret agent hired by a state to obtain information about its enemies or by a business to obtain industrial secrets from competitors