Definition of officer noun from the Oxford Advanced Learner's Dictionary
officer
noun
ˈɒfɪsə(r) ˈɔːfɪsər ˈɑːfɪsər
1a person who is in a position of authority in the armed forcesarmy/airforce/naval, etc. officersa commissioned/non-commissioned officerThe matter was passed on to me, as your commanding officer. see also flying officer, petty officer, pilot officer, warrant officer2(often in compounds) a person who is in a position of authority in the government or a large organizationan environmental health officera customs/prison/welfare officerofficers of state (= ministers in the government) see also chief executive officer, medical officer, press officer, probation officer, returning officer3(often used as a form of address) = police officerthe officer in charge of the casethe investigating officerYes, officer, I saw what happened.4(North American English) a title for a police officerOfficer Dibble
ˈɒfɪsə(r) 
ˈɔːfɪsər 
1 a person who is in a position of authority in the armed forcesarmy/airforce/naval, etc. officersa commissioned/non-commissioned officerThe matter was passed on to me, as your commanding officer. see also flying officer, petty officer, pilot officer, warrant officer