Some dude named Adam Jacot de Boinod scoured foreign dictionaries for words that lack a precise equivalent in the English language and gathered the best ones into a book, The Meaning of Tingo: And Other Extraordinary Words from Around the World. According to Amazon, the book will not be available in the US until next March.
For a sneak preview, the review from The Independent offers a selection of these words. Here are some highlights:
mamihlapinatapei is from the Fuengian language in Chile, meaning "a shared look of longing between parties who are both interested yet neither is willing to make the first move"
tingo, from Easter Island's Pascuense language, means "borrowing things from a friend's house, one by one, until he has nothing left"
pomicione is Italian for "a man who seizes any chance of being in close physical contact with a woman"
senzuri is the Japanese word for male masturbation, or literally "a hundred rubs"—compare the word for women's good times, shiko shiko manzuri, literally "ten thousand rubs" (did they get the math right?)
fucha is a Portuguese verb meaning "to use company time and resources for one's own purposes"
buz-baz is ancient Persian for "a showman who makes a goat and monkey dance together"
mata ego, from Rapa Nui, Easter Island, means "eyes that reveal that someone has been crying"
desus is Indonesian for "the quiet, smooth sound of somebody farting but not very loudly," which I always thought was spelled pssssssffft
seigneur-terrasse is the French term for "someone who spends time, but not money, at a café"
And the beautiful xiaoxiao is Chinese for "the whistling and pattering of rain or wind"
(Thanks to Elise at After School Snack for the lead.)
Update: The folks at Language Log, as usual, have more on the topic.