I think that the confusion here is not Augustine but Webster. Many of us grew up with words having less than subjective meanings (those of us 40 years old or older, anyway). We also had to memorize multiplication tables because those didn't change either. But time....now that's different. That changes and we simply have to learn to change with it.No, it's not "oxymoronic"...
"lose" would be a statement of conditionality............
"eternal" would be a temporal statement of duration.
It's so simple...
But no Calvinist preacher wants to teach you the difference. (if they even know it).
There's no oxymoron there...but far be it from logic, reason or the Scriptures to threaten Augustinianism.
Back in my day this is how eternal was defined:
Eternal – without beginning or end; lasting forever; opposed to temporal
But back in my day if we invented our own meanings we would get a whooping from the teacher, and another when we got home. They stifled our creative self-expression back then and forced us into a narrow box called "reality". That's why we are pretty good at our jobs but not so good at video games. And that's why we do not understand "eternal life" to be a temporary sort of thing.