Using smart keywords as described in the link, you can make it so that if you type ‘d nonplussed’ into Firefox’s address bar to do a lookup in your favourite dictionary site, or ‘th nonplussed’ for a thesaurus lookup, or ‘wp nonplussed’ for a Wikipedia lookup etc. Combine this with the alt-d hotkey to move the cursor to the address bar, and you can lookup an unfamiliar word in literally 2 seconds, which means you’re way more likely to do it. After using it for a while, you’ll be saying more really big words, which among other things is totally sexy.

… although they say it’s not the size of your vocabulary that matters, it’s how you use it.