stubborn
chitonous
deep-thinking
inexpugnable
insubmissive
meek-looking
non-persistent
old-young
pre-programmed
self-asserting
self-engrossed
self-limitation
self-righteously
small-minded
so-long
steel-grey
uncompromised
unelastic
unpliant
unsubmissive
untameable
unterrified
untired