This is a subheading of Liber VII and there are zero references to this on the Internet other than the title of the book. And yes obviously it stands for Egytptian Kabballah but there are only two sources to this term anywhere, once in the subtitle of Liber VII and once where the subtitle appears in Magick In Theory and Practice.
Also full text is Adumbratio Kabbalae Aegyptiorum:
From Latin adumbrō (“I cast a shadow upon”, “I sketch”, “I imitate or counterfeit”). “Egyptian qaballah”