The term WATCH SECRETLY can be summarized by two crossword solutions: SPY (3 letters) and SPYON (5 letters). SPY is a noun that refers to a person who secretly observes and gathers information on others, usually for political or military purposes. SPYON is a verb that means to observe or investigate someone or something secretly. Both words are related to the concept of espionage, which is the practice of spying or using spies to obtain secret information.