The English-Italian Dictionary on WordReference has two English-Italian dictionaries.
The Pocket Oxford Italian Dictionary has 90,000 words and phrases with 120,000 translations. It is a high-quality dictionary from one of the world’s most respected publishers.
The WordReference English-Italian Dictionary is a living, growing dictionary. It contains over 50,000 terms and 100,000 translations in both English and Italian and continues to grow and improve. In Italian-English, thousands more terms that are not included in the main dictionary can be found in the WordReference Italian-English forum questions and answers.
If you still can not find a term, then you can ask in the forums where many native English and Italian speakers from around the world love assisting others to find the right translation.
Give it a try at: http://www.wordreference.com/iten/