can't speakUsually appears as part of 말을 못 하다, meaning “to be unable to speak” or “to be unable to say something.” Depending on context, it can indicate physical inability, lack of language ability, or being unable to bring oneself to say something.
KO: 긴장해서 하고 싶은 말을 못 했어요.
EN: I was too nervous to say what I wanted to say.