Final answer:
The word that is a synonym for frighten in the given lines is 'scare'
Step-by-step explanation:
In the given lines from the poem, the speaker is expressing a fear or being scared. The word 'frighten' is used to convey this emotion. A synonym for frighten in this context would be 'scare' as it represents the same feeling of fear or being frightened.
Learn more about synonyms for frighten