If you hit "return" after launching eXL (and you've either selected a word in eXs before launching eXL, or typed a word into the Search box of eXL), then you'll get back an extensive definition of the word.
Clicking on a word or phrase in the Definition area and hitting any of the buttons next to the Search bar will:
1) Perform the button's function on the word, and...
2) Add the word to the Word List, which can be saved with the Session.