A Yiddish word that means, literally, to wish someone well, to delight in someone else's delight. It's the opposite of envy and schaudenfreude.
Moe: Hey, did you hear the news? Curly got a perfect score on his SAT and he didn't even study!
Larry: That stinks. I studied for weeks and I still bombed.
Moe: You mean you're not happy for him? Where's your sense of farginen?