Officer Of"fi*cer, n. [F. officier. See Office, and cf. Official, n.] 1. One who holds an office; a person lawfully invested with an office, whether civil, military, or ecclesiastical; as, a church officer; a police officer; a staff officer. ``I am an officer of state.' --Shak. 2. (U. S. Mil.) Specifically, a commissioned officer, in distinction from a warrant officer. Field officer, General officer, etc. See under Field, General. etc. Officer of the day (Mil.), the officer who, on a given day, has charge for that day of the quard, prisoners, and police of the post or camp. Officer of the deck, or Officer of the watch (Naut.), the officer temporarily in charge on the deck of a vessel, esp. a war vessel.