I found this in Wikipedia.
A dry enema is an alternative technique for cleansing the human rectum either for reasons of health, or for sexual hygiene. It is accomplished by introducing a small amount of sterile lubricant into the rectum, resulting in a bowel movement more quickly and with less violence than can be achieved by an oral laxative.
It is called "dry" by contrast to the more usual wet enema, because no water is used.
A rudimentary form of 'dry' enema is the use of a non-medicated glycerin suppository. However due to the relative hardness of the suppository - necessary for its insertion into the human body - before the glycerin can act, it must be melted by the heat of the body, and hence it does not take effect for up to an hour. Often the hygroscopic glycerin irritates the sensitive membranes of the rectum resulting in forceful expulsion of the suppository without any laxative effects.
A quicker form of the dry enema utilizes the injection of a small amount of water-based lubricant such as K-Y into the rectum via a non-hypodermic syringe, such as an oral syringe, or from some other source.
The usual amount of lubricant applied is about 2 tsp (10 cc), which will produce a movement in 30 minutes or less. The movement will be produced in a compact body, rather than in the more copious liquid form produced by a wet enema; and since no water is used, none will be retained higher up in the colon, to be expelled at a later, and possibly inconvenient, time.
A further advantage of this technique for sexual hygiene is that any slight remaining traces of fecal material will - due to the presence of the lubricant - tend to adhere to the wall of the rectum rather than to any foreign object which may subsequently be inserted.