to relax - via sexual intercourse, the use of a dildo, fist, or other object - an anus to the point where it will remain open, at least for a short while, when the penis or dildo is removed. This is a desirable goal in certain kinds of fetishist anal play, e.g. the open anus is considered visually exciting, or it can be urinated in, used during scat play, etc. Sometimes "medical" devices, such as a speculum, are used to keep the anus open for similar purposes.
Something often used in anal pornography. When an object, such as a mans penis, is inserted into someone's anus, stretching it, then it being removed and the anus remaining open, meaning it's possible to see inside