to be petrified; to be unable to move; to be paralyzed (with horror); to be stupefied (with amazement)
急な大声に彼女は立ち竦んだ。
She froze at the sudden loud voice.
事故現場を前に彼はただ立ち竦んでいる。
He is just standing there frozen in front of the accident scene.
恐怖で立ち竦む感覚を誰でも経験する。
Everyone experiences the sensation of being paralyzed with fear.