This is a much maligned term. It is as wrong to abuse the license this provides by blatting as it is to ignore the indication entirely. The best description I've heard of the sound is that of "sizzle" in the sound. It is still a dark and focused sound, but with a bit of an edge at the extreme loud end of the dynamic range. The best way to get an idea of what is acceptable is to hear it done. If you are lucky enough to live near a quality orchestra go hear them play. If not, get some recordings. I highly recommend recordings of the Vienna Philharmonic for this, but that's just my personal taste.