From high + -ish.
highish (comparative more highish, superlative most highish)
- Somewhat high.
2008 January 27, Terrence Rafferty, “Doesn’t Scare Easily”, in New York Times[1]:Reading Barron, though, I realized that part of the reason his stories leave me cold is that they assume, as too much genre fiction does, a highish level of reader credulity, and I resent it.