A Fleeb- someone who hates Hegarty maths and uses it for memes not maths.
Snoobing- putting a computer mouse on its side because you are that Edgy.
Twettut- to react like an octopus when you are not
Smebe- someone who knows none of the above things.
Everyone but the spassorps is a smebe.
Unfortunately, there isn't an easy way (you can't just type in a number of syllables or number of letters); you'll have to edit the rules.
Click "(show rules)" if the list of rules isn't visible. Then you'll have to edit the line starting with "WORD ="; this is a list of options separated by |. If you want a length that the program already sometimes generates, you can delete the other options. If you want something longer, look at whatever the longest option is and use that. (If you see something like *2, that just modifies the probability for choosing that option.)