to freeze (from fear, etc.); to be unable to move (e.g. from surprise); to be paralyzed (with horror, etc.)
to cower; to shrink in on oneself
熊を見て足が竦んだ。
My legs froze when I saw the bear.
突然の音に子供は竦んで動けない。
The child is frozen and can't move due to the sudden sound.
兵士は目の前の惨状に恐怖で身が竦むものだ。
A soldier's body often freezes in terror at the devastation before his eyes.