There are 13 words that start with 'exterm'.
| extermine | extermined | 
| extermines | exterminate | 
| extermining | exterminated | 
| exterminates | exterminator | 
| exterminating | extermination | 
| exterminators | exterminatory | 
| exterminations | |
Note: These 13 words that start with 'exterm' are found from the USA & Canada version of the tournament Scrabble word list.