What does the term "Speed" mean in a speaker?

I believe it is all things that come together to have a fast set of speakers. Well designed paper drivers in a well design enclosure . With as high end crossovers as you can afford , with an amplifier with the appropriate taps , bi amplified . I think fast is what we are all trying to achieve . A speaker doing precisely what it is told . 

@obelisk- "Some speaker designers used to put the tweeters physically behind the plane of the woofer to try and accomodate the slower response of the woofer." No- The physical time alignment, in multi-driver systems, has nothing to do with the relative speed of the drivers. Rather: to get the acoustic centers(actual sound source/voice coil) of the drivers, in the same plane/in phase. https://en.wikipedia.org/wiki/Loudspeaker_time_alignment

Great discussion and lots of good info to consider. At the end of the day, it’s what one hears. I have experienced speakers that are fast but didn’t sound it because of bass overhang attributable to room acoustics. Fix the room and you’ll extract everything the speakers can offer. And also be confident when evaluating new speakers. I have a really good room acoustically and whe I compared new Raidho speakers to my existing Burmesters (both ribbon tweeters) I could really feel the impact of the transients. Not sure I would have before getting my room right. Just my opinion.