What does fao mean

What does fao mean?

I think you mean FAU
which is the default name when a user is either deleted or selects their question or answer to be anonymous. It stands for FunAdviceUser

xox
Sika

It depends in what context you mean.
Usually it means 'For the Attention Of'

It can also mean;

FAO Financial Aid Officer
FAO Faro, Portugal - Faro (Airport Code)
FAO Fatty Acid Oxidation
FAO Federal Approving Official
FAO Federal Archaeology Office (Canada)
FAO Field Air Only (paintball)
FAO Field Artillery Operator
FAO Field Audit Office (DCAA)
FAO Finance & Accounting Office(r)
FAO Finish All Over
FAO Fire Apparatus Operator
FAO First Africa Oil Plc (London, UK)
FAO Fiscal Affairs Office (EU)
FAO Fiscal Agent Organization (healthcare)
FAO Fishermen's Advocacy Organization
FAO Flight Activity Officer
FAO Floating Atomic Orbital
FAO Flugbüro Am Opernplatz (now FAO Travel)
FAO Food and Agriculture Organization (United Nations)
FAO Forced Air Oil
FAO Foreign Area Officer
FAO Formation Assistée par Ordinateur
FAO Forward Air Observer
FAO Frederick August Otto (Schwarz; FAO Schwarz toy stores)
FAO Ford Automotive Operations

Hope that helped.