Occupation: Airline Pilot
Rank: First Officer
Role: Co-pilot.
^^ sounds good to me.
Also, Co-Pilot: a fully qualified pilot who shares duties at the pointy end of the aircraft with the captain but is not the legal commander (unless the latter is incapacitated). This is pretty unambiguous to me.
Just like a First officer is second-in-command of the aircraft to the captain...but because of various airline schemes to pay less, distinctions of rank such as Junior First Officers, First Officers, Senior First Officers, Second Officers, Relief-qualified First Officers etc have become popular...