I was almost afraid to buy a Kobo after reading so much about how bad their dictionary was. So far, every word that I've looked up has been there, so... yay.
Anyhow, I just saw a word that I didn't know:
nacreous
So, I clicked it. I get this definition:
"possessing the qualities of, consisting of, or abounding in nacre"
Grrr.... I hate those definitions. On my Kindle PW1, with the latest firmware that it received (maybe they're better now), that was it -- dead end. But on the Kobo I was able to click on a word in the dictionary and get a definition of that word! I hold down on nacre, and I get:
mother-of-pearl
Yay! That I know! That said, once I got to that secondary dictionary view, I could no longer click, though I was in a search interface where I could type the words if I needed to.