As an ESL (English as a second language) instructor, I often tell my students to avoid using translating dictionaries and to try understanding new English words by learning synonyms, paying attention to context, and by listening to or reading lots of examples from native speakers.
The Huffington Post recently came out with a list of Spanish words for which there may be no single comparable English word. Since I'm not bilingual, I can only trust that the translations to English are as close as possible to the meaning of the words in Spanish. As with English, the main problem of providing a single definition for these Spanish words is that other meanings are possible, e.g., sobremesa (could be a tablecloth or dessert). The most common usage of a word is usually the only one provided in paperback translating dictionaries. Even when searching online for definitions in English, there are many dictionaries and definitions to choose from. Language is very much a reflection of culture (previously touched on here), so it's not surprising that there may be no single word equivalence between languages. Translation always requires interpretation of one culture's vocabulary into the standard of another. If Facebook is any indicator of how far we have to go with translating apps, we still have a looong way to go with non-European languages such as Arabic, Korean, and Japanese.