Did you miss where they do that by sterilization? And qualities of a race or breed?
Do you speak English? Is this a translation error?
Edit to add-
And you present it like there’s multiple definitions. There is not. This is Merriam’s entry-
the practice or advocacy of controlled selective breeding of human populations (as by sterilization) to improve the populations’ genetic composition
The second one is for kids. The follow on context under the actual definition also makes it very clear that this was selective breeding by sterilization, closely related to white supremacy ideology.