involuntary

involuntary
/ɪnˈvɔləntrɪ; ?@ -terɪ; ɪn`vɑlənˌtɛrɪ/ adj
done without intention; done unconsciously 非有意的; 无意的; 无意识的; 不自觉的
    an involuntary movement of surprise, eg jumping when startled 因吃惊而引起的不自觉的动作（如吓得跳起来）. Cf 参看 voluntary1.

牛津英汉双解词典