EasyDefine is a site I just found out about from the amazing educator/presenter/app designer, Ozge Karaoglu. This is a terrific site for uploading a list of words to get their definition. However, what makes EasyDefine so great are various formats in where you can get your results such as: definitions, synonyms, flash cards, and quizzes. All which are ideal for learning your words.
I highly recommend checking out EasyDefine by clicking here!!
For another great site for learning Vocabulary check out SpellingCity.