An Injaculation is an ejaculation that is forced backward, so instead of squirting out the urethra, it is blocked. Depending on where and how it is blocked, the cum might flow past the sphincter valves and into the bladder. The next urination is typically cloudy, and sometimes has clumps of semen. The ejaculation doesn’t always make it into the bladder. It may simply be retained in the prostate area, and is eventually absorbed by the body.
Points for blocking, to cause an injaculation are:
1. At the tip of the penis. Pinching the glans closed during ejaculation does reduce the mess that would otherwise be created, but is not a real injaculation, because the semen remains in the distal portion of the urethra until released. Sometimes a man who has his ejaculation blocked with a pinched glans will discover the orgasmic contractions last longer, even much longer. For some men, this is painful, as the urethra is stretched just behind the block.

The million-dollar spot
2. Between the anus and the base of the scrotum in the area known as the perinium. This requires fairly firm pressure with one or two fingers, and they must be directly over the urethra. This interesting effect can cause a true injaculation. Experimentation is usually required to find just the right place to press. The exact place to press is sometimes called ‘the million-dollar spot.’
3. Near the base of the penis, just forward of the scrotum. This is a cross between true injaculation and pinching the glans, generally resulting in the semen flowing out as soon as the pressure is released.
4. Psychological/physiological: It is possible to resist an ejaculation, but for most men it is very difficult. A tantric practice called the big draw can be effective.
The medical profession is divided on support of injaculation. Some say it is dangerous, possibly causing symptoms, although most never quite say what those symptoms would be. Others will tell you that they, or others, have been practicing it for thousands of years without ill effect.
Injaculation has been used as a low-reliability version of birth control.