Glosbe - Huge collaborative massively multilingual dictionary.
Duolingo - Duolingo is a free language learning app for iOS, Windows and Android devices. The app makes learning a new language fun by breaking learning into small lessons where you can earn points and move up through the levels. Read more about Duolingo.
Visuwords - The fun and free way to look up definitions. THE graphical dictionary and visual thesaurus.
Touco - Toucan is a small portableapp utility allowing you to synchronise, backup and secure your data with...
Wordnik - the biggest online English dictionary, by number of words
Mondly - Learn 33 languages in 500 bite-size lessons and 14 conversational modules.