unsubstantiated

他的演讲缺乏具体数据支持。

His speech was ___unsubstantiated with concrete data.

这些谣言完全没有根据，却传播得很快。

The rumors were completely ___unsubstantiated yet spread quickly.

他的借口听起来很空洞，没有任何实质内容。

His excuse sounded ___unsubstantiated and lacked any real content.