Initially, in the world of the characters in the novel, the A stands for adultery. The meaning, however, changes as the plot progresses and some in the story regard the A as meaning angel. From the...
i.e. stands for "in essence"...
You may be referring to Id Est, Latin for 'that is'.
"Access Server", "Aortic stenosis", "Adult swim" and "ActionScript"
"[Windows] Millennium Edition", "Memory Effect" and "Myalgic Encephalomyelitis"