To my understanding, the characterization of an aorta as an "aneurysm" versus a "dilation" refers to how much greater the diameter of the aorta is than normal. The exact numbers depend on which part of the aorta is being evaluated. I believe the term "aneurysm" is used when the ascending aorta is greater than 4.5 cm and "dilated" when it's between 4.0 and 4.5 cm

You can try to unravel it here: https://www.ahajournals.org/doi/10.1161/CIR.0000000000001106. This document is very technical and directed at physicians though. I'd have to guess that "enlarged" is ... high end of normal? Slightly above normal?