How to describe the size of this garden faucet fixture?
That is a bog-standard boiler drain valve. 1/2" Male Pipe Threads (which are larger than 1/2", as 1/2" is the size of the hole in the pipe) on the inlet and Garden Hose Threads on the outlet.

You can also get a "frost free hose bibb" also called a sillcock which has a much longer body so that the actual valve and male pipe thread is inside the building while the hose thread and handle are on the outside of the building, but that would presumably require changing the pipes it's connected to.