Recently one of my correspondents asked me the Spanish word for paragliding. Probably I'd heard it before, but I couldn't think of it, and my big Collins dictionary didn't have it. So I looked up 'paragliding' in Wikipedia, and when the English page came up I then switched over to the Spanish version of the same page. Bingo, there was my translation: 'el parapente'.
As there are Wikipedia pages in many languages, this is a rather general-purpose method, although it's mainly useful for nouns and for the more popular languages. There are Wikipedia pages in, say, Punjabi and Tibetan, but not very many pages.