The word "terror-struck" denotes a state of extreme fear or panic. Antonyms for terror-struck include words like calm, composed, collected, and relaxed. These words indicate a sense of peacefulness or serenity. Other antonyms can include brave, courageous, and confident, which suggest a sense of strength and bravery. Words like untroubled, unruffled, and undisturbed can also act as antonyms, indicating that the individual is not affected emotionally by a potentially frightening situation. Ultimately, the opposite of being terror-struck is to feel safe, secure, and in control of one's emotions.