A bridge officer was an officer whose station or main duties took place on the bridge of a starship. A group of bridge officers were collectively known as the bridge staff.
In 2366, Picard ordered Riker to "assemble the bridge staff for a mission briefing in fifteen minutes." (TNG: "Tin Man")
For a bridge officer to be eligible to take command, the Bridge Officer's Test had to be passed. (TNG: "Thine Own Self")
Even acting ensigns, such as Wesley Crusher, could be bridge officers. (TNG: "Where No One Has Gone Before", "Hide And Q", "Coming of Age")
If a non-bridge officer and a bridge officer held the same rank, the bridge officer was considered the ranking officer. (VOY: "Displaced")
In 2374, Ixtana'Rax threatened to kill all the USS Defiant bridge officers if there was the slightest sign of treachery. (DS9: "One Little Ship")
During The Doctor's legal proceedings against Broht & Forrester, Harry Kim testified that thanks to command subroutines being added to his program, "in an emergency, he's as capable as any bridge officer." (VOY: "Author, Author")