Webster's Revised Unabridged Dictionary · 1913

Spy

Spy (spī) , transitive verb

[Old English spien, espien, Old French espier, French épier, Old High German spehōn, German spahen; akin to Latin specere to see, Sanskrit spac. r 169. Compare Espy, transitive verb, Aspect, Auspice, Circumspect, Conspicuous, Despise, Frontispiece, Inspect, Prospect, Respite, Scope, Specimen, Spectacle, Specter, Speculate, Spice, Spite, Suspicion.]

1.
To gain sight of; to discover at a distance, or in a state of concealment; to espy; to see.
One, in reading, skipped over all sentences where he spied a note of admiration. — Swift
2.
To discover by close search or examination.
Look about with your eyes; spy what things are to be reformed in the church of England. — Latimer
3.
To explore; to view, inspect, and examine secretly, as a country; -- usually with out.
Moses sent to spy out Jaazer, and they took the villages thereof. — Num. xxi. 32

Spy , intransitive verb

To search narrowly; to scrutinize.
It is my nature's plague To spy into abuses. — Shakespeare

Spy (spīz) , noun

[See Spy, v., and compare Espy, n.]

1.
One who keeps a constant watch of the conduct of others.
These wretched spies of wit. — Dryden
2.
(Military) 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.
Collocations (2)
Spy money , money paid to a spy; the reward for private or secret intelligence regarding the enemy.
Spy Wednesday (Ecclesiastical) , the Wednesday immediately preceding the festival of Easter; -- so called in allusion to the betrayal of Christ by Judas Iscariot.