I don’t think you can argue that Chazal had a different definition for ??? ???? without running afoul of the next question in the Gemara: ?”? ???? ????? ??? ??? ???? ????? ?? ???? ???”? ??? ????? ????? ??? ???? ????? ???? ??? ?????? ???? ????? ?????? ????? ????? ????? ???? ??? ?????? ???? ?????
Abaya asks that how can the Chachomim say that that lice ???? ??? ???? when there is a posuk that refers to lice eggs? The Gemara answers that according to the Chachomim you have to say that it means a creature called “lice eggs” but not the eggs of lice. If the Gemara had a different definition of ??? ????, it would have answered “lice have eggs but they are still not ??? ???? because ??? ???? means X.”
Hilchos Shabbos is not an area where I have expertise (neither is hilchos Treifos) but I believe it is machlokis acharonim whether killing lice today is mutar.