To indicate the threshold or level above which something will become unacceptable or will provoke a response; to create a boundary and imply or declare that its crossing will provoke a (negative) response.
To lay down a challenge; to provide a test of commitment (often one which carries a high risk) to a cause.
To create a real or artificial boundary or distinction between (two places, people or things).
To elicit a response.
To call out; to draw out or bring forth.
To cause the manifestation of something (emotion, picture, etc.) in someone's mind or imagination.