According to SOWPODS (the combination of Scrabble dictionaries
used around the world) there are 12 words with the pattern -UD-ER.
That is, six letter words with 2nd letter U and 3rd letter D and
5th letter E and 6th letter R. In alphabetical order, they are:
budder
budger
dudder
judder
judger
mudder
mudger
nudger
pudder
rudder
sudder
sudser