What does "performant" software actually mean?
performance, terminology
Solution
In university, performant means that you have an optimal solution in O(n) notation. You might get a remark on your paper about using made up words instead of the proper terminology though.
In business, performant means that your customer hasn't complained about the speed (yet). Your product is also buzzword compliant.
Problem
I see it used a lot, but haven't seen a definition that makes complete sense. Wiktionary says "characterized by an adequate or excellent level of performance or efficiency", which isn't much help. Initially I though performant just meant "fast", but others seem to think it's also about stability, code quality, memory use/footprint, or some combination of all those. I think this is a "real" question - but if enough people reckon this is a subjective question, that's an answer in itself.