Scrabble words

I've just had 'avizes' played against me.  This word isn't defined in any Scrabble dictionary I could find (though it is agreed to be in SOWPODS).  Even the OED couldn't find it!

I've just played 'roon' which  I freely admit was a guess to try and use up my last three letters and end the game, but at least it's a real word!  (a remnant of cloth, usually involving the selve-edge)

What puzzles me is how some of the words that aren't in any dictionary I can find are still able to get into the Scrabble word lists.

I've discovered that my local library allows me online access to the OED.  This is a good thing.