How to present a large amount of terms

I am currently working on a project where I have about 15 terms and doing it in RISE but also didn't want to just use the accordion. I am adding a Storyline block in with a 9 rectangle grid, and then each one will flip to a full layer of content (as the definitions are long) with a x in top right to close it and return to the grid.  The grid rectangles visited state will change.  I will probably build two blocks.  I worry it may be too much of selecting the x to close them but those are my thoughts.  So, I welcome ideas as well :)