n. 1 a person who observes. 2 an interested spectator. 3 a person who attends a conference etc. to note the proceedings but does not participate. 4 a a person trained to notice and identify aircraft. b a person carried in an aeroplane to note the enemy's position etc.
OBSERVER
Meaning of OBSERVER in English
Concise Oxford English dictionary. Краткий оксфордский словарь английского языка. 2012