Well, I was introduced to the word via that site, but was sorta hoping for a general definition, whether referring to Kilmichael or elsewhere. Still, thank you. That seems like a pretty good guess, at least regarding that area, specifically. Does it appear in other sites or anywhere that isn't part of a proper name, does anyone know?

You're right about the 'green' link. There is one other source for 'glas' in an (Irish at least) placename and that's the one pronounced 'glash' meaning a stream, but was often transliterated as 'glas' because the English couldn't tell one accent from another!