I learned today that the most untranslatable word in the world is "ilunga". It is a Tshiluba word for a person who is ready to forgive any abuse for the first time; to tolerate it a second time; but never a third time. Tshiluba is a Bantu language spoken in south-eastern Congo, and Zaire.
The most untranslatable words in English are below.
1. Plenipotentiary: a diplomat who is fully authorized to represent his or her government
2. Gobbledegook: an English term used to describe nonsensical language, sound that resembles language but has no meaning, or encrypted text
3. Serendipity: good luck in making unexpected and fortunate discoveries
4. Poppycock: stuff: senseless talk
5. Googly: a cricket ball bowled as if to break one way that actually breaks in the opposite way
6. Spam: To indiscriminately send unsolicited, unwanted, irrelevant, or inappropriate messages, especially commercial advertising in mass quantities. Noun: electronic "junk mail".
7. Whimsy: an odd or fanciful or capricious idea
8. Bumf: toilet paper (often used for printed matter that might as well be used as toilet paper)
9. Chuffed: very pleased
10. Kitsch: art that is considered to be overly sentimental, pretentious design