http://rewordify.com/ is a terrific site for helping students improve their vocabulary.
When students are researching a topic and come upon information that may be difficult to understand, they can copy and paste that information into Rewordify. Instantly, the difficult vocabulary will be reworded in more understandable terms. Students can click each highlighted section to see the original vocabulary. Here is a terrific 3 min. video on Rewordify! There are a ton of potential applications of this terrific site. What are your ideas?