Mishnayos Shabbos Perek 19 Mishnah 6

ציצין –hidden shreds of flesh that remain from the foreskin.

עטרה – it is a tall rim which surrounds the membrum virile round about and from it slants and descends to its head and the skin that covers most of the corona of the membrum virile as our Mishnah teaches , one should not say most of the coagulation, but even most of its height in one location.

אינו אוכל בתרומה – if he is a Kohen, for an uncircumcised Kohen is prohibited to eat the priest’s due/Terumah. It is said regarding the Passover sacrifice (Exodus 12:45): “No bound or hired laborer shall eat of it,” and it is stated regarding Terumah (Leviticus 22:10): “No bound or hired laborer of a priest shall eat of the sacred donations.” Just as the Passover offering is prohibited to someone uncircumcised, so too the Terumah is prohibited to someone uncircumcised.

ואם היה בעל בשר – if he was fat and flesh appeared that was above his uncircumcised membrum, after the foreskin was taken off completely, as if the flesh returned and covered the membrum virile.

מתקנו – and he slants the cutting utensil/knife from that thickness [of the fat].

מפני מראית העין – so that he would not appear as uncircumcised.

ולא פרע – and he did not reveal it.

כאלו לא מל – and he would go back and split the membrane and pull it down and even if he removed his hand from it – for all the while that he is engaged in the circumcision on the Sabbath, he cuts whether the remaining shreds invalidate the act by omission or whether they don’t invalidate the act by omission after he removes his hand from the shreds which invalidate the act, he returns to the shreds which do not invalidate the act and he doesn’t go back.