You can describe someone as noncommittal when they deliberately do not express their opinion or intentions clearly.
例句
Mr Hall is non-committal about the number of jobs that the development corporation has created...霍尔先生并未明确说明开发公司已创造的岗位数量。Sylvia's face was noncommittal...西尔维娅一脸不置可否。
英汉词典释义
adj.
不作许诺的;不表态的
I asked him if he approved of our plan, but he was noncommittal.我问他是否赞同我们的计划，但他态度不明朗。‘Billy, I think it’s your turn to wash the dishes,’ said Jane. A noncommittal grunt was his only reply.“比利，我想这次该轮到你刷盘子了， ”简说。他只是不置可否地咕哝了一声算作回答。