spying — a person employed by a government to obtain secret information or intelligence about another, usually hostile, country, especially with reference to military or naval affairs.
intelligence — capacity for learning, reasoning, understanding, and similar forms of mental activity; aptitude in grasping truths, relationships, facts, meanings, etc.
surveillance — a watch kept over a person, group, etc., especially over a suspect, prisoner, or the like: The suspects were under police surveillance.
shadowing — a dark figure or image cast on the ground or some surface by a body intercepting light.
tailing — the hindmost part of an animal, especially that forming a distinct, flexible appendage to the trunk.
secret service — the branch of governmental service that conducts secret investigations, especially investigations into the military strength of other nations.
