What does nonspecific t abnormalities on lateral leads mean on an ecg?

Medical Diagnostics. This is simply that the t waves seen on this ECG were not normal but they were also not diagnostic of any condition. Ekgs have specific changes that correlate with specific and commonly seen cardiac damage. This is just a way of saying there is nothing here that explains any disease. It is not to be worried over.
Truly: nothing!! Non-specific t waves changes are just what they sound like: non-specific! they can be normal for you or caused by anything such as hyperventilation, low potassium, magnesium, calcium; they can come and go. They don't diagnose any actual condition. It's just a descriptive phrase that means, "not quite the way it would look in a textbook.". Fear not!
T abnormalities. As the description says, they are non specific and do not cause alarm by themselves and need to be correlated with clinical symptoms.