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 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 make difficult to accomplish; to act as an obstacle; to frustrate.
To delay or impede; to keep back, to prevent.
Of or belonging to that part or end which is in the rear or hind, or which follows.
The buttocks.