What does "Sounds too Hifi" mean???

...it's when you don't know how to describe precisely or more specific or haven't enough vocabulary or combination of all above you can say instead: "HiFi", "NotHiFi", "NotTooHiFi" and "TooHiFi"...

accentuated highs & boomy bass is sometimes associated with that vernacular "too hi fi" when compared to a more desirable flat response

"Too HiFi" most often connotes: "I can't afford it", "I regret my last upgrade" or "I really like it but I'm not supposed to".

too much transparency,detail, and realism...

I like the "I can't afford it" comment. I would also like to add stereos that are "too hifi" are only sold in snooty stereo boutiques.

Actually, I think "too hifi" is a misnomer. What I mean is, there is no such thing as too much hifi. Either you like a stereo system or you don't.

If there is a stereo that does everything perfectly, yet you just have don't have subjective preference towards this system, then the label "too hifi" is used.

That subjective preference can come in many different vehicles. That system doesn't evoke quality within the perception of the individual buyer, or that buyer simply has cold feet (or cold ears?).

In summary, there can be infinite # of subjective reasons why an otherwise adequate stereo is "too hifi."