Firm, Stout, Sturdy
noun, な adjective
A stubborn height is a shorter, stockier height. It makes a person especially solid, firm, and stout.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
You should make the foundation as firm as possible.
This car is solidly built.
I had a really solid pair of glasses made by my optician.