Lexigo - Instant Dictionary by Jort

Lexigo is an instant, in-browser dictionary that makes reading online smoother and more enjoyable. By default, you can look up any word with a simple double click, but you can also configure it to require holding down a key to avoid accidental lookups.

Each time you look up a word, Lexigo saves it along with its definition, giving you a personal library of terms you have explored. This list can be downloaded at any time for study or reference, and you can reset it whenever you want to start fresh.

Lexigo supports a wide range of languages, namely: Arabic, Chinese (Simplified), Dutch, French, German, Greek, Hebrew, Italian, Norwegian, Polish, Portuguese, Russian, Spanish, and Turkish.