Wabi and Sabi
I do like a good German word for something for which English has no equivalent. But I have lately expanded that beyond German into Japanese. I have the guy who sits across from me at work to thank for sending me down this path. Boy can he talk. I have to try to remember to only engage in speaking to him when I have time for the ensuing conversation, which it is usually very interesting and informative. He studied urban landscapes and design and is passionate about architecture and history ... I don't know what he is doing here working on the boringest among boring products, but none of us knows what we're doing here.
Recently, after the cold weather brought it out, he held up the Dr Who scarf that he knitted himself and asked me if I could spot the mistake, which, unfortunately, I could, but he then told me that was the "wabi" - and on we went with a conversation about wabi and whatever else. It would seem that wabi has had a number of different meanings over time, but the sense in which my colleague was using it is below. The meanings of wabi and sabi have also since been combined into this Japanese world view or kind of spirituality called (you guessed it) Wabi-sabi, about finding beauty in imperfection and simplicity etc, which is something else again.

Wabi
Japanese noun. A flaw that gives elegance and uniqueness to the whole. This can be as simple as the tiny crack in one's favorite cup. It can also be handmade books or dinners that you've made from scratch. Everyone's face has wabi.
Sabi
Japanese noun. The patina of age, such as the softness of worn granite or the browning in one's favorite tea cup. It refers to the natural progression of time, and carries with it an understanding that all things will grow old and become less conventionally beautiful.
I took most of this from here (leaving out the sweeping cultural generalisations), and added to it from about the place.