Another term for low sperm count.
Basically saying when a male doesn't have a high sperm count, or when the sperm dies before reaching the egg, it's nearly
impossible to father a child with a female. There have been cases when a male with a low sperm count can actually father a child, but for many others, it's
impossible unless their female
counterpart is highly fertile or when one of the sperm actually does make it to the egg.