Scrabble words

I'm playing four or five games of Scrabble at present, and several times now, I've thought - well, that sounds like a plausible word, let's check it out in the dictionary. 

So, I look it up in the dictionary and get the really irritating reply that  "This word exists in the Scrabbulous dictionary, but we do not have a definition for it"

Two other online dictionaries that I try don't know it either.

eg. 'bien' is in my son's copy of 'Scrabble Words' and in SOWPODS  online (though not in TWL, so I can't actually play it in any of my current games), but what does it mean?

I like to play words that I know the meaning of!