Sleuth
Part of speech: verb
Definition: To act as a detective; to try to discover who committed a crime.
Part of speech: noun
Definition: An animal's trail or track. A sleuth-hound; a bloodhound. A detective. Slowness; laziness, sloth. A collective term for a group of bears.
Spy
Part of speech: noun
Definition: A person who secretly watches and examines the actions of other individuals or organizations and gathers information on them (usually to gain an advantage)
Part of speech: verb
Definition: To act as a spy.To spot at a distance.
Example sentence: To get a FISA warrant to spy on a suspected spy, the feds go before a super-secret court located in a sealed room in the Department of Justice. With no defense lawyers present, they need only show probable cause that the target is an 'agent of a foreign power' engaged in intelligence gathering against the United States.