1. Noun. A gay man, not overly flamboyant, but with particular tastes or likings. Acronym for Gay Eccentric Man
2. Adj. A characterist or trait of a female who does nice things for others.
1) I.e. Seth is such a GEM. He won't bed down with boyfriends in cheap hotel rooms like the Atlantis.
I.e. Isn't he a GEM? He likes Crown and diet to drink because it's sweet, and he feels it is a masculine drink that won't ruin his figure.
2) I.e. Brittany is such a GEM. She's willing to help anyone out without question.
I.e. Isn't she a GEM? She just helped that old man across the street.