To keep a long story short. I did indeed download this
list of 170,000 words. I then saved it as a RTF file and converted it to EPUB with Calibre. I did run into a glitch which is explained
here.
After sorting out the conversion issue, I had a 2.2M EPUB file. The file though lagged and crashed on my Nook. I'm now redoing the EPUB file and splitting it up into much smaller files. So far I have A-B, C-D, E-H and I-L on my Nook. It could probably be done in one sitting but it's a little tedious and because of weekend plans, I didn't have time to finish it. I found that if I broke up the words into smaller paragraphs, it helps with the lagging.
In short, yes, it works. I open up the file with the starting letter, type the word in "find" and then put the Nook dictionary to work. There still seems to be about 1 or 2 second lag but the files do not crash my Nook.
I did a few test runs and there were some words missing from the list. But that's understandable for a list with only 170K entries. There are also words on the list that the Nook dictionary couldn't cover. Meh, for now this works as a makeshift dictionary to look up random words. I'll be happy to pay for a fully functional EPUB dictionary (can't believe it's not available for sale!) or if/when Nook allows us to access the built-in dictionary freely.