“What does "slow is smooth, smooth is fast" mean?”

I disagree slightly with the other two answers (so far).

I heard this saying from my U.S. Marine son, and the way it was explained to he and I, was that performing a critical task correctly and completely and exactly (i.e. taking the amount of time required to do all those things) would always overall, have better results in a shorter time, than hurrying to perform the same task, concentrating on speed alone.

This resonated with what I had already learned from studying old Western “gunslingers” (the ones who won). The successful shooters all agreed that it was not the fastest gun who won battles, it was the most accurate shooter.

Another way to say this, would be that the overall fastest way to complete a task or challenge, is to perform it as EFFICIENTLY as possible. And efficiency is at it’s maximum, when all actions involved are performed smoothly.

In short, it’s not a matter of just slowing down to LEARN a procedure, and then speeding up, it is actually faster overall, to do any procedure smoothly, even from the first time you do it.