What It Scores
XYLYL is a valid word in the tournament list this site uses. Tile values only, before any premium square: 18 in Scrabble and 18 in Words With Friends. The letters break down as X8 Y4 L1 Y4 L1.
Longer Words Containing XYLYL
XYLYL 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.