presumptuous
/prɪˈzʌmptʃuəs; prɪ`zʌmptʃʊəs/ adj
(a) (of a person or his behaviour) too bold or self-confident （指人或其行为）胆大妄为的, 放肆的, 冒失的, 专横的
Would it be presumptuous of me to ask you to contribute? 可否冒昧请求你出一份力?
(b) (of a person) acting without the necessary authority （指人）自行其是的, 自作主张的
He was presumptuous in making the announcement before the decision had been approved. 决议尚未通过他已径自宣布.