There are 15 words that start with 'unstr'.
| unstrap | unstraps | unstress |
| unstring | unstrung | unstrings |
| unstriped | unstrained | unstrapped |
| unstressed | unstresses | unstrapping |
| unstringing | unstratified | unstructured |
Note: These 15 words that start with 'unstr' are found from the USA & Canada version of the tournament Scrabble word list.