DY,
What is another possible definition?
Also, the current scientific knowledge is that lice are hatched from eggs. So even if you have some way of explaining the Gemara so that it isn’t presuming spontaneous generation, you would still need to explain the need for the dochek on ???? ?????.
I also don’t understand the Chazon Ish you are citing (noting that Treifos is not a sugya I have ever learned). The list of Treifos are a halacha l’Moshe m’Sinai, why would it depend on the metziyus at the time of Chazal and not the metziyus at the time of Matan Torah?