At first I didn't see the point, what with many other online dictionaries out there, but some insight is given on the "Read why he built it." page (http://eightpence.com/ninjawords-a-fast-online-dictionary-fast-like-a-ninja/)

...I’ve built an online dictionary because I was frustrated with what’s out there. I often need to quickly check a word’s definition, and I usually find myself shouting these questions at the websites (I sometimes take bad usability personally):

* Why are you inundating me with images and ads, when the content of dictionaries are purely text?!
* Do you really think I ...

At first I didn't see the point, what with many other online dictionaries out there, but some insight is given on the "Read why he built it." page (http://eightpence.com/ninjawords-a-fast-online-dictionary-fast-like-a-ninja/)

...I’ve built an online dictionary because I was frustrated with what’s out there. I often need to quickly check a word’s definition, and I usually find myself shouting these questions at the websites (I sometimes take bad usability personally):

* Why are you inundating me with images and ads, when the content of dictionaries are purely text?!
* Do you really think I need to see 50 definitions of the same word?
* Why do I have to open 10 separate pages to look up 10 different words?
...
With Ninjawords, looking up a word doesn’t cause a page refresh. And it
tells you it’s doing something (”looking up [word]”), which is
reassuring when you have a slow connection like mine. You can look up
many words on the same page, either one at a time or separated by
commas. You can look up words by URL in case you don’t want to navigate
to the page once itself, which can save some time.