[ams6110]

That's not exactly what "free" means in an economic context, but probably doesn't alter your point.

Something is "free" if, at a price of zero, there is enough supply to meet demand.

[dmichulke]

Interesting definition.

It follows that nothing is universally free, it can only be free within spatial (and probably temporal) constraints. The usual candidates (water, air) are certainly not free everywhere.