The Collaborative International Dictionary of English v.0.48:
Spy \Spy\, n.; pl. Spies (sp[imac]z). [See Spy, v., and cf.
1. One who keeps a constant watch of the conduct of others.
"These wretched spies of wit." --Dryden.
2. (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.
Spy money, money paid to a spy; the reward for private or
secret intelligence regarding the enemy.
Spy Wednesday (Eccl.), the Wednesday immediately preceding
the festival of Easter; -- so called in allusion to the
betrayal of Christ by Judas Iscariot.
Syn: See Emissary, and Scout.
Easton's 1897 Bible Dictionary:
When the Israelites reached Kadesh for the first time, and were
encamped there, Moses selected twelve spies from among the
chiefs of the divisions of the tribes, and sent them forth to
spy the land of Canaan (Num. 13), and to bring back to him a
report of its actual condition. They at once proceeded on their
important errand, and went through the land as far north as the
district round Lake Merom. After about six weeks' absence they
returned. Their report was very discouraging, and the people
were greatly alarmed, and in a rebellious spirit proposed to
elect a new leader and return to Egypt. Only two of the spies,
Caleb and Joshua, showed themselves on this occasion
stout-hearted and faithful. All their appeals and remonstrances
were in vain. Moses announced that as a punishment for their
rebellion they must now wander in the wilderness till a new
generation should arise which would go up and posses the land.
The spies had been forty days absent on their expedition, and
for each day the Israelites were to be wanderers for a year in
the desert. (See ESHCOL.)
Two spies were sent by Joshua "secretly" i.e., unknown to the
people (Josh. 2:1), "to view the land and Jericho" after the
death of Moses, and just before the tribes under his leadership
were about to cross the Jordan. They learned from Rahab (q.v.),
in whose house they found a hiding-place, that terror had fallen
on all the inhabitants of the land because of the great things
they had heard that Jehovah had done for them (Ex. 15:14-16;
comp. 23:27; Deut. 2:25; 11:25). As the result of their mission
they reported: "Truly Jehovah hath delivered into our hands all
the land; for even all the inhabitants of the country do faint
because of us."