A person who makes entries into the offbeat children's website Urban Dictionary urbandictionary.com
Normally, they are individuals who think they are far funnier than they actually are, entries to the dictionary often reflect this.
They sometimes vary in forms and one may come across the pisstaker variety, whereby they make an entry in the urban dictionary, simply to ridicule other urban dictioneers.
It is somewhat a mystery how urban dictioneers are capable of converting electronic writing into actual excrement.
please see previous entry for an example of an urban dictioneer