[Jack Sawyer]

I tend to think of 'realism' along a spectrum from 'possible' to 'likely'. Closer to the end of 'possible is' 'it can occur by our understanding of science however unlikely or theoretical' - this can often be just a hair under 'pseudoscience' but many people will often believe it is real all the same (see: cold fusion, the EM Drive.) 'Likely' is what we often think of for the hardest of the Hard sci fi, where you are trying to apply science as rigorously and extensively as you can and it may be largely 'near future' stuff and little else. Somewhere in between those extremes you could have 'plausible' which is a bit more rigorous than 'possible' but it doesn't go to the extreme that 'likely' does, although the precise point along the aforementioned spectrum will vary according to perception.