What It Scores
DUD is a valid word in the tournament list this site uses. Tile values only, before any premium square: 5 in Scrabble and 6 in Words With Friends. The letters break down as D2 U1 D2.
Longer Words Containing DUD
DUD appears inside each of these, which is what makes it worth knowing as a hook.
Next: the Word Unscrambler for any letters at all, and the two and three letter lists. Full entry and definition at Merriam-Webster.