Unity freezes temporarily when recompiling/refreshing scripts

In the editor, there is a little animated icon in the lower right that indicates it is active but compiling. Is that actually animating or is it frozen?

This can occur in projects with a large code-base. Obviously your computer resources effect compile time as well but even a computer with good specs can take a while to compile a large project. I am currently working on game that takes my Mac about 10-15 seconds to compile, with ~5 seconds of that time being the editor "frozen". When the editor freezes like this due to a compile you should still see the animated "compile" spinner in the bottom right corner, it is just frozen like the rest of the editor.

Something you can do to help reduce this is convert any framework code to compiled libraries (dlls). Since your code is already compiled in a dll, Unity shouldn't recompile it.

If your project isn't that big then I am not sure what else this could be.