In real life, the flexibility illustrated by touching one's toes, or doing the splits on two trucks is totally irrelevant.
The flexibility that will help you not only fight well should you be called to do so, but also live well is not best described by that word. At 58 (180-190 depending on training) and pretty strong, I could not do the splits or kick someone in the head...but I can squat 350 and deadlift 450. I can also instinctively relax and move if I need to. A few months ago I wrote about tripping on something and transferring into a forward roll without a thought...and I am not a Judo guy. I also wrote about the Shield maiden throwing the dog's ball and me evading it without analyzing.
Suppleness?
Adaptability?
I don't know...but flexibility is not what describe what we are looking for here. I think it is a far better thing to be able to deadlift 2.5 times your bodyweight than to be able to do the splits...but maybe that is just me...although I have done both at one time or another.
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