What It Scores
MUMU is a valid word in the tournament list this site uses. Tile values only, before any premium square: 8 in Scrabble and 10 in Words With Friends. The letters break down as M3 U1 M3 U1.
Words Made From The Letters In MUMU
6 shorter words come out of these tiles. On a board that matters more than the long play, because a short word on a premium square often beats a long one on plain squares.
3 letter words (3)
2 letter words (3)
Longer Words Containing MUMU
MUMU appears inside each of these, which is what makes it worth knowing as a hook.
Next: the Word Unscrambler for any letters at all. Full entry and definition at Merriam-Webster.