Something that is suffocating makes you feel uncomfortably hot or unable to breathe.

I've got to open the window - it's suffocating in here! 我得把窗户打开——这里太闷了！

suffocating smoke/fumes 令人窒息的烟／烟雾

preventing something or someone from improving or developing in a positive way

The book tells the story of a woman escaping from a suffocating marriage. 这本书讲的是一个女人逃脱一段令人窒息的婚姻的故事。

It is a land of antiquated social rules and suffocating traditions. 这个地方依然保留着陈规陋习和令人倍感压抑的传统习俗。