to make something more difficult to deal with, do, or understand

It will only complicate the situation if we invite his old girlfriend as well. 如果我们同时也邀请他以前的女友，只会使事情更加复杂。

The rescue operation has been complicated by bad weather. 恶劣的天气使救援工作变得更加艰难。

These new rules have complicated the tax system even further. 这些新规定使税收制度更加复杂。

If one illness complicates another illness, it makes the other illness worse.

The breathing problem has now been complicated by a chest infection. 因为胸腔感染，他的呼吸问题变得更加严重了。