A WikiWord is made up of two or more concatenated words with uppercase letters (this is often also referred to as CamelCase). If you write a word this way into a page of the WikiWikiWeb, you create a new HyperLink.
These are valid WikiWords for example:
while those are not:
You can also create HyperLinks inside your WikiWikiWeb which are not made up of WikiWords by using square brackets:
Sometimes you must be a bit creative to invent nice and talking WikiWords, but this can also be very funny.