This is the 13603rd most frequent Russian word.
недоговаривать
To not say everything; to leave something unsaid.
The word 'недоговаривает' here means that the subject does not fully express all the necessary information.
Он всегда недоговаривает что-то важное.
He always leaves out something important.
In this sentence, 'недоговаривает' is used to imply that the subject intentionally omits parts of their speech.
Мне кажется, она специально недоговаривает.
I think she intentionally doesn't say everything.
The word 'недоговаривает' suggests that the speaker believes the other person is withholding information.