staff officer n (Military) a commissioned officer serving on the staff of a commander, service, or central headquarters Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014staff? of`ficer n. a commissioned officer who is a member of a military staff. [1695?1705] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.