There are 15 10-letter words that start with 'woo'.
| woodblocks | woodborers | woodchucks | 
| woodcrafts | woodcutter | woodenhead | 
| woodenness | woodenware | woodgrains | 
| woodlander | woodpecker | woodstoves | 
| woodwaxens | woodworker | woolliness | 
Note: These 15 10-letter words that start with 'woo' are found from the USA & Canada version of the tournament Scrabble word list.
Also see words start with wood, wool, woof, wooz, woos, woop, woor, wooe, wooi, woom.
4-letter words start with 'woo' (4)