How can a field definiton be imported, either via the admin or in code? In my admin one of the modules I have installed (I am not sure which) has the ability to export a field definition in code, but I can't see any place where I can import the field. I thought that the field creation dialog has abilty to import a field definition from the export code just as the bundle creation tool give the ability to import a bundle.

There is no such thing in the menu and I wonder if I am missing something in the interface or I have to resort to code.

Is there something missing in the admin interface, or do I have to import it in code?
There is nothing in the interface but what you can do is make a temporary content type which uses the field(s) you wish to import, then export/import that content type to the target site.

Your new field(s) will then be available at the target site, make sure you attach them to other content types before you delete the temporary one or the field(s) will disappear.