What does it mean to have my stress test result be borderline abnormal?

You need a nuclear 1: women have more noise in conventional ekg stress tests. For this reason for a lot of years it was recommended to give dye studies (nuclear stress tests). Frankly all of stress tests fell a bit out of favor except for risk forcasting so we didn't care so much whether it worked. But the dye study gives much more accurate results in women.

Many different thing: There are many different reasons for a stress test to be abnormal. That doesn't mean there is actually any concerning cardiac issue at hand, but can be related to normal anatomic variants, technical issues with the procedure itself, baseline abnormal electric abnormalities of your ecg, and other factors too. unfortunately without more information regarding your testing it's hard to be specific.