There are 12 words that start with 'rereg'.
| reregister | reregulate | 
| reregisters | reregulated | 
| reregulates | reregistered | 
| reregulating | reregulation | 
| reregistering | reregulations | 
| reregistration | reregistrations | 
Note: These 12 words that start with 'rereg' are found from the USA & Canada version of the tournament Scrabble word list.