I saw goosh the other day, which is a prototype pseudo-commandline interface to the web. It seemed to be missing a dictionary lookup function, but did appear to have an extension load function.
So I had a look at the goosh source javascript, which had a comment that pointed to a plugin example, which is a snippet of unformatted code with no docs. With a bit of poking around and experimentation, I managed to create a plugin that looks up words on wiktionary.
To try this out, go to goosh and type:
guest@goosh.org:/web> load http://hewgill.com/~greg/dict.js
Then, use the dict command (or wiktionary or d as listed in the help) to open the wiktionary page for the given word in a new window.
Perhaps there will be a way to load a goosh extension in a persistent way so you don't have to reload it every time you reload goosh itself.