Par*rhe”si*a\, n. [NL., fr. Gr. ?; ? beside, beyond + ? a speaking.] (Rhet.) Boldness or freedom of speech.
Foucault (Fearless Speech, 1983) sums up the Ancient Greek concept of parrhesia as such:
So you see, the parrhesiastes is someone who takes a risk. Of course, this risk is not always a risk of life. When, for example, you see a friend doing something wrong and you risk incurring his anger by telling him he is wrong, you are acting as a parrhesiastes. In such a case, you do not risk your life, but you may hurt him by your remarks, and your friendship may consequently suffer for it. If, in a political debate, an orator risks losing his popularity because his opinions are contrary to the majority’s opinion, or his opinions may usher in a political scandal, he uses parrhesia. Parrhesia, then, is linked to courage in the face of danger: it demands the courage to speak the truth in spite of some danger. And in its extreme form, telling the truth takes place in the “game” of life or death. (p.15-16)
To summarize the foregoing, parrhesia is a kind of verbal activity where the speaker has a specific relation to truth through frankness, a certain relationship to his own life through danger, a certain type of relation to himself or other people through criticism (self-criticism or criticism of other people), and a specific relation to moral law through freedom and duty. More precisely, parrhesia is a verbal activity in which a speaker expresses his personal relationship to truth, and risks his life because he recognizes truth-telling as a duty to improve or help other people (as well as himself). In parrhesia, the speaker uses his freedom and chooses frankness instead of persuasion, truth instead of falsehood or silence, the risk of death instead of life and security, criticism instead of flattery, and moral duty instead of self-interest and moral apathy. (p.19-20)