<p><strong>Noun</strong></p><ul><li>someone or something that observes.</li><li>a delegate to an assembly or gathering, who is sent to observe and report but not to take part officially in its activities.</li><li>U.S. Air Force: a member of an aircrew, other than the pilot, holding an aeronautical rating.</li><li>a person who maintains observation in an aircraft during flight.</li><li>Also called air observer.</li><li>U.S. Army: a person who serves in an aircraft as a reconnoiterer and directs artillery fire.</li></ul>