spy

Concise Oxford English Dictionary © 2008 Oxford University Press:
spy/spʌɪ/

▶noun (pl. spies)

• 1 a person employed by a government or other organization to collect and report secret information on an enemy or competitor.

• 2 a person who observes others secretly.

▶verb (spies, spying, spied)

• 1 be a spy.

  ■ (spy on) observe furtively.

• 2 observe or notice.

– phrases
spy out the land collect information about a situation before deciding how to act.

– origin ME: shortening of OFr. espie ‘espying’, espier ‘espy’, of Gmc origin.