A conversational phrase used to introduce an honest or frank opinion (equivalent to "to be honest" or "frankly").
正直言って、彼の料理はあまり美味しくなかった。
To be honest, his cooking wasn't very good.
正直言って、まだその仕事に自信がありません。
Honestly, I'm still not confident about that job.
正直言って、どう思う？
Frankly, what do you think?
正直言って、彼女の意見に賛成できない。
To be frank, I can't agree with her opinion.