spy

Etymology

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.

noun

1. A person who secretly watches and examines the actions of other individuals or organizations and gathers information on them (usually to gain an advantage).
   Even without hovering drones, a lurking assassin, a thumping score and a denouement, the real-life story of Edward Snowden, a rogue spy on the run, could be straight out of the cinema. But, as with Hollywood, the subplots and exotic locations may distract from the real message: America’s discomfort and its foes’ glee. 2013-06-29, “Travels and travails”, in The Economist, volume 407, number 8842, page 55
2. (American football) A defensive player assigned to cover an offensive backfield player man-to-man when they are expected to engage in a running play, but the offensive player does not run with the ball immediately.

verb

1. (intransitive) To act as a spy.
   During the Cold War, Russia and America would each spy on each other for recon.
2. (transitive) To spot; to catch sight of.
   I think I can spy that hot guy coming over here.
   One in reading, skipped over all sentences where he spied a note of admiration. 1720, Jonathan Swift, A Letter to a Young Clergyman
   Child, I see thee! Child, I spy thee! 1818, John Keats, A Prophecy
   The next person they spied was a Bandicoot carrying a watermelon. 1918, Norman Lindsay, The Magic Pudding, page 68
3. (intransitive) To search narrowly; to scrutinize.
4. (transitive) To explore; to see; to view; inspect and examine secretly, as a country.