I think that's what bugs me about "performant" --- it feels like vague buzzwordy management-speak, because there's already a well-understood word for the same concept: "fast". Ditto for "lightweight"; "small" gets the point across clearly, and if it's both fast and small, it's "efficient".

Software can be big or small, fast or slow, efficient or inefficient (for combinations of size and speed.) I don't think we need any more adjectives beyond those.

Instead of "significantly less performant", you could just say "much slower". (Note that LOOP was much slower on older Intel CPUs, but was the same as the longer sequence on AMD's. It would not surprise me if newer Intel ones now decode LOOP into the same sequence of uops. In any case, unless the loop is a tiny one, what happens in the body is likely to make a much more significant difference, especially if cache misses are involved.)

Some interesting reading on why LOOP was slower on Intel CPUs --- because Windows 95's timing loop used it (observe the lack of "performant" in any of those posts): https://groups.google.com/d/topic/alt.windows98/liuMAIctHRg

A vague word is useful when you are trying to convey a vague concept, in much the same way as it would be hard to convey the idea that you know that some metric is between 20% and 40%, if you are not allowed to be vague and are required to arbitrarily pick some number like 38.51% and say that one instead

What's imprecise about: "Performant: 1) meeting the objective, often applied to a performance objective, 2) productive"?

In looking around just now, economics seems to prefer the second definition, which is why I added it. All of the uses I found are compatible with this definition.

What's the definition of "object oriented" again?