1
general::
Phrase(s): *rooted to the spot
Fig. unable to move because of fear or surprise. (*Typically: appear to be ~; be ~; become ~.) • Jane stood rooted to the spot when she saw the ghostly figure. • Mary stood rooted to the spot when the thief snatched her bag.
McGrawhill's American Idioms And Phrasal Verbs
2
general::
Not moving, especially owing to some strong emotion. For example, When the truck bore down on the dog, he was terrified and stood rooted to the spot. This idiom likens the roots of a plant to a strong feeling that keeps one from moving.
American Heritage Idioms