My plumber has said we need a spigot fitted before the concrete floor goes in , what is a spiggot

Another name for a faucet or a tap. I can see why piping may need to go in but not a faucet. What is his reason?

A spigot usually refers to an outside type faucet (hose-bib or sillcock are other names).

Venturing a guess that this is new construction, I'm thinking the plumber is telling you that you need a spigot of some kind available for the concrete guys... guys need water and need to attach a hose to something.

Of course, as Ma0641 suggested, you need to clarify things with the plumber!

Mark

What your plumber wants to install is a hosebib (see image). Good luck, Tom