Offtopic: As I continue to lament the fact that Apple has strengthened the virtual padlocks securing their latest mobile phone, I noticed an opportunity for me to create a lexicon list. As they say, opportunity doesn't strike twice (or was that lightning), so I'm here to make the most of it. :)
Disclaimer: Every site mentioned here was endorsed by at least one digg user in this digg, Definr: Super Fast Dictionary You Haven't Used Before, and I'm not about to take credit or vouch for them.
Let's start off with the site that started it all - definr. Touted as an "incredibly fast dictionary", definr is particularly proud of its ultrafast (O(log(n)) for autocomplete, O(n log(n)) for lookup) algorithm. Sadly, it's based solely on Princeton's open WordNet 2.0, which apparently has only 236,973 words at the moment. Expect more definitions to be added as they implement support for other databases. Check out definr's tools to accelerate your search even further.
"A really fast dictionary... fast like a ninja" pretty much sums up Ninjawords. With Wiktionary and Wordnet as its source, Ninjawords will hit you with sharp definitions before you know it. To become a full fledged ninja word searcher, consult Ninjaword's tips.
ObjectGraph AJAX DictionaryCreated in Dec 2004, ObjectGraph AJAX Dictionary is probably the oldest dictionary on this list. Don't be fooled by its age though, it can easily match the speed of its newer counterparts. ObjectGraph AJAX Dictionary provides a wide variety of search results as it relies on 6 separate reference sources.
I haven't got a clue who created Clue. All I know is Clue's rather rapid and returns proper usage of a word along with its definitions.
WordWeb OnlineWordWeb Online is the online version of WordWeb, a Windows based dictionary/thesaurus software. On its own, it contains only about 300,000 words and phrases, but it is able to intelligently redirect you elsewhere if it can't find a word. As WordWeb doesn't contain ads or images, searches are quite quick even though it doesn't use AJAXy search-as-you-type.
These are just the first 5 super fast dictionaries recommended by digg users. Return tomorrow for more super fast dictionaries!