fornication with ... Egyptians - alliances with Egypt, cemented by sharing their idolatries.
great of flesh - of powerful virile parts; figuratively for the gross and lustful religion of Egypt (for example, Isis, etc.), which alone could satisfy the abominable lust of Israel (Eze 20:7, Eze 20:8; Eze 23:19, Eze 23:20, Eze 23:21).