There are 9 words that start with 'stupef'.
| stupefy | stupefied | 
| stupefier | stupefies | 
| stupefiers | stupefying | 
| stupefaction | stupefyingly | 
| stupefactions | |
Note: These 9 words that start with 'stupef' are found from the USA & Canada version of the tournament Scrabble word list.