Lexicon is a word look-up program for validating the existence of words in specific word lists. This is the first QML Harmattan application by developer Andrew Olmsted (@fiferboy)
Add the repo to your "/etc/apt/sources.list.d/community.list" file. (NOTE: this file does not exist by default)
Add the following line:
deb http://repo.pub.meego.com/home:/fiferboy/Harmattan/ ./
Then run (as root or the nearest equivalent):
apt-get install lexicon
If you don't want to add a repo you can download the file and install it separately. Keep in mind you won't get automatic updates to the package.
For further information, please head on over to Fiferboy's Developing