I'll take a jab at this word from the audiophile dictionary.
A revealing speaker has elevated treble response. -Revealing more detail in the music. It's certainly not neutral and will thus be best with certain music genre.
The revealing speaker funnily enough is missing details in the high/mid/low bass area while still being described as revealing.
The revealing speaker is, when the listener is not in the mood or the track is anything else than easy jazz or audiophile acoustics, also typically described as "fatigueing" "forward", "bright", "cold", "sterile", "thin".