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

"You can't be serious."
https://www.thefreedictionary.com/read+between+the+lines

Don't get out much? Sorry, couldn't resist.

"Maybe you're number 1?"
https://en.m.wikipedia.org/wiki/Snowflake_(slang)#Generation_Snowflake

Oh my, are you one of these? If not, refer back to above.

Interesting discussion. +1 on many posts. Nods to @simonmoon and similar posts and to @mikelavigne ’s points.

Adding an aspect that hasn’t been brought up...reduction in system noise.

I personally believe that the speed of bass tends to be slower than the highs because it can take longer for the waves to start energising the air due to their longer wavelengths. YMMV

"You can’t be serious."
https://www.thefreedictionary.com/read+between+the+lines

Don’t get out much? Sorry, couldn’t resist.

"Maybe you’re number 1?"
https://en.m.wikipedia.org/wiki/Snowflake_(slang)#Generation_Snowflake

Oh my, are you one of these? If not, refer back to above.

1. Stop wasting people time.
2. Stop making dumb post.
3. Maybe you should get out ... of here lols.  

Erik, yes speakers interact with the room but that has nothing to do with the transient response on the speaker.
Mike, unfortunately regular dynamic drivers are a poor impedance match to air. They have to work much harder to get the job done. ESLs and Horns do not have this problem to near the degree.
ESLs and horns are generally described as being very detailed. They also have better transient response, association or causation. I would say the later. Yes, a speaker with a lighter moving system could have better transient response assuming the motor was designed correctly. 
Andy, resolution and transient response are very closely related. By dynamic I do not mean loud. I mean snap.