Κέφι (kefi) is one such greek word. The word is actually borrowed from the turkish (keyif) -credit where it's due- and I think it means more or less the same thing in both languages. However I can only really speak for the greek usage.
It is a word worn a lot. I can't find
one word in another language to describe it. It means having fun, being in a good mood, being full of joy of life, being drunk, feeling exuberant, doing something with zeal and passion... It is very difficult to define, as it ranges from just a good mood to rather passionate extremes. It is also used in many different expressions. Not having κέφι means "I'm not in the mood (right now)", I'm feeling listless, bored. Coming to κέφι means reach a state of merriment, often by drinking. Κάνω (do,make) κέφι someone or something means fancy someone, fancy doing something. Doing something with κέφι means you are doing it with passion. Having κέφια (plural) means being in a very good mood. You can be κεφάτος (kefatos -with kefi) or άκεφος (akefos - without kefi), or when you meet someone, you can ask "how are the kefia?" (πώς παν' τα κέφια; ) as a more casual "how are you". The rather stupid custom of smashing plates is considered an expression of kefi, when the soul and body are overwhelmed with an exuberance that must find an outlet. (that last sentence except for the "rather stupid" part is taken from the definition in
about.com)