Indeed, FireFly is correct in definition.
However, the number that will now call Ops for an adjustment to FOB when checking the weather, normally to save 2-3 mins of paperwork, leads me to believe they do not have the courage of their convictions in requesting said fuel, or more importantly, cannot be bothered to report, through proper channels, a trend to monitor requiring more fuel.
It is a thin line, we all put petrol in our cars, we all know it is expensive. It is to be carried in 'excess of PLOG' when the Commander sees fit, therefore the Commander can justify, please take the time to do so, sometimes, airport, runway changes etc Operational experience, he will be assisting others and justifying his/her position as 'Aircraft Manager'
Likewise, when presented with a computer generated round trip tanker PLOG, don't take another 5 tonne because it is cheap, it isn't anymore.
Above all, fly safe, your experience is valuable to your employer and those you mentor, F/O's, ground staff and the dreaded beancounters I hope.